Maemo "optification" was added

[gnuplot] / docs / gnuplot.texi

\input texinfo   @c -*-texinfo-*-

@c %**start of header
@setfilename gnuplot.info
@settitle Gnuplot: An Interactive Plotting Program
@setchapternewpage odd
@c %**end of header

@c define the command and options indeces
@defindex cm
@defindex op
@defindex tm

@dircategory Math
@direntry
* GNUPLOT: (gnuplot).             An Interactive Plotting Program
@end direntry

@ifnottex
@node Top, gnuplot, (dir), (dir)
@top Master Menu
@end ifnottex

@example
                       GNUPLOT

            An Interactive Plotting Program
             Thomas Williams & Colin Kelley
          Version 4.2 organized by: Hans-Bernhard Broeker

 Copyright (C) 1986 - 1993, 1998, 2004   Thomas Williams, Colin Kelley

       Mailing list for comments: gnuplot-info@@lists.sourceforge.net
     Mailing list for bug reports: gnuplot-bugs@@lists.sourceforge.net

         This manual was originally prepared by Dick Crawford
                   Version 4.2 - 1 Oct 2006


Major contributors (alphabetic order):
@end example

@c ^ <h2> An Interactive Plotting Program </h2><p>
@c ^ <h2>  Thomas Williams & Colin Kelley</h2><p>
@c ^ <h2>  Version 4.2 organized by Hans-Bernhard Broeker and others</h2><p>
@c ^ <h2>Major contributors (alphabetic order):</h2>

@itemize @bullet
@item
Hans-Bernhard Broeker
@item
John Campbell
@item
Robert Cunningham
@item
David Denholm
@item
Gershon Elber
@item
Roger Fearick
@item
Carsten Grammes
@item
Lucas Hart
@item
Lars Hecking
@item
Thomas Koenig
@item
David Kotz
@item
Ed Kubaitis
@item
Russell Lang
@item
Alexander Lehmann
@item
Alexander Mai
@item
Ethan A Merritt
@item
Petr Mikulik
@item
Carsten Steger
@item
Tom Tkacik
@item
Jos Van der Woude
@item
Alex Woo
@item
James R. Van Zandt
@item
Johannes Zellner
@end itemize

@c ^<h2>  Copyright (C) 1986 - 1993, 1998 - 2004   Thomas Williams, Colin Kelley<p>
@c ^   Mailing list for comments: gnuplot-info@@lists.sourceforge.net <p>
@c ^   Mailing list for bug reports: gnuplot-bugs@@lists.sourceforge.net <p>
@c ^</h2><p>
@c ^<h3> This manual was prepared by Dick Crawford</h3><p>
@c ^<h3> Last revised: February 2007</h3><p>
@c ^<hr>

@menu
* gnuplot::                     
* Commands::                    
* Terminal_types::              
* Graphical_User_Interfaces::   
* Bugs::                        
* Concept_Index::               
* Command_Index::               
* Options_Index::               
* Function_Index::              
* Terminal_Index::              
@end menu

@node gnuplot, Commands, Top, Top
@chapter gnuplot


@menu
* Copyright::                   
* Introduction::                
* Seeking-assistance::          
* New_features_introduced_in_version_4.2::  
* Backwards_compatibility::     
* Features_introduced_in_version_4.0::  
* Batch/Interactive_Operation::  
* Command-line-editing::        
* Comments::                    
* Coordinates::                 
* Datastrings::                 
* Environment::                 
* Expressions::                 
* Glossary::                    
* linetype::                    
* mouse_input::                 
* Plotting::                    
* Start-up::                    
* String_constants_and_string_variables::  
* Substitution_and_Command_line_macros::  
* Syntax::                      
* Time/Date_data::              
@end menu

@node Copyright, Introduction, gnuplot, gnuplot
@section Copyright

@cindex copyright

@cindex license

@example
    Copyright (C) 1986 - 1993, 1998, 2004, 2007  Thomas Williams, Colin Kelley

@end example

Permission to use, copy, and distribute this software and its
documentation for any purpose with or without fee is hereby granted,
provided that the above copyright notice appear in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation.

Permission to modify the software is granted, but not the right to
distribute the complete modified source code.  Modifications are to
be distributed as patches to the released version.  Permission to
distribute binaries produced by compiling modified sources is granted,
provided you
@example
  1. distribute the corresponding source modifications from the
   released version in the form of a patch file along with the binaries,
  2. add special version identification to distinguish your version
   in addition to the base release version number,
  3. provide your name and address as the primary contact for the
   support of your modified version, and
  4. retain our contact information in regard to use of the base
   software.
@end example

Permission to distribute the released version of the source code along
with corresponding source modifications in the form of a patch file is
granted with same provisions 2 through 4 for binary distributions.

This software is provided "as is" without express or implied warranty
to the extent permitted by applicable law.


@example
      AUTHORS

@end example

@example
      Original Software:
         Thomas Williams,  Colin Kelley.

@end example

@example
      Gnuplot 2.0 additions:
         Russell Lang, Dave Kotz, John Campbell.

@end example

@example
      Gnuplot 3.0 additions:
         Gershon Elber and many others.

@end example

@example
      Gnuplot 4.0 additions:
         See list of contributors at head of this document.

@end example

@node Introduction, Seeking-assistance, Copyright, gnuplot
@section Introduction

@cindex introduction

@c ?
`gnuplot` is a command-driven interactive function and data plotting program.

Any command-line arguments are assumed to be names of files containing
`gnuplot` commands, with the exception of standard X11 arguments, which are
processed first.  Each file is loaded with the `load` command, in the order
specified.  `gnuplot` exits after the last file is processed.  The special
filename "-" is used to denote standard input.  When no load files are named,
`gnuplot` enters into an interactive mode.  See help for `batch/interactive`
for more details.

`gnuplot` is case sensitive (commands and function names written in lowercase
are not the same as those written in CAPS).  All command names may be
abbreviated as long as the abbreviation is not ambiguous.  Any number of
commands may appear on a line (with the exception that `load` or @ref{call} must
be the final command), separated by semicolons (;).  Strings are indicated
with quotes.  They may be either single or double quotation marks, e.g.,

@example
      load "filename"
      cd 'dir'

@end example

although there are some subtle differences (see `syntax` for more details).

Many `gnuplot` commands have multiple options. Version 4 is less sensitive
to the order of these options than earlier versions, but some order-dependence
remains. If you see error messages about unrecognized options, please try
again using the exact order listed in the documentation.

Commands may extend over several input lines by ending each line but the last
with a backslash (\).  The backslash must be the _last_ character on each
line.  The effect is as if the backslash and newline were not there.  That
is, no white space is implied, nor is a comment terminated.  Therefore,
commenting out a continued line comments out the entire command
(see `comments`).  But note that if an error occurs somewhere on a multi-line
command, the parser may not be able to locate precisely where the error is
and in that case will not necessarily point to the correct line.

In this document, curly braces (@{@}) denote optional arguments and a vertical
bar (|) separates mutually exclusive choices.  `gnuplot` keywords or @ref{help}
topics are indicated by backquotes or `boldface` (where available).  Angle
brackets (<>) are used to mark replaceable tokens.  In many cases, a default
value of the token will be taken for optional arguments if the token is
omitted, but these cases are not always denoted with braces around the angle
brackets.

For on-line help on any topic, type @ref{help} followed by the name of the topic
or just @ref{help} or `?` to get a menu of available topics.

The new `gnuplot` user should begin by reading about `plotting` (if on-line,
type `help plotting`).

See the simple.dem demo, also available together with other demos on the web page
@uref{http://www.gnuplot.info/demo/simple.html,http://www.gnuplot.info/demo/simple.html
}

@node Seeking-assistance, New_features_introduced_in_version_4.2, Introduction, gnuplot
@section Seeking-assistance

@c ^ <a name="Seeking-assistance"></a>
@cindex help-desk

@cindex seeking-assistance

There is a mailing list for `gnuplot` users.  Note, however, that the
newsgroup
@example
      comp.graphics.apps.gnuplot
@end example

is identical to the mailing list (they both carry the same set of messages).
We prefer that you read the messages through the newsgroup rather than
subscribing to the mailing list.  Instructions for subscribing to gnuplot
mailing lists may be found via the gnuplot development website on SourceForge
@uref{http://sourceforge.net/projects/gnuplot,http://sourceforge.net/projects/gnuplot
}

The address for mailing to list members is:
@example
      gnuplot-info@@lists.sourceforge.net

@end example

Bug reports and code contributions should be mailed to:
@example
      gnuplot-bugs@@lists.sourceforge.net

@end example

The list of those interested in beta-test versions is:
@example
      gnuplot-beta@@lists.sourceforge.net

@end example

There is also the canonical (if occasionally out-of-date) gnuplot web page at

@uref{http://www.gnuplot.info,http://www.gnuplot.info
}

Before seeking help, please check the

@uref{http://www.gnuplot.info/faq/,FAQ (Frequently Asked Questions) list.
}

When posting a question, please include full details of the version of
`gnuplot`, the machine, and operating system you are using.  A _small_ script
demonstrating the problem may be useful.  Function plots are preferable to
datafile plots.  If email-ing to gnuplot-info, please state whether or not
you are subscribed to the list, so that users who use news will know to email
a reply to you.  There is a form for such postings on the WWW site.


@node New_features_introduced_in_version_4.2, Backwards_compatibility, Seeking-assistance, gnuplot
@section New features introduced in version 4.2

@cindex new-features

@c ?version 4.2 features
Gnuplot version 4.2 offers many new features introduced since the preceding
official version 4.0. This section lists major additions and gives a partial
list of changes and minor new features. For a more exhaustive list, see the
NEWS file.


@menu
* New_plot_styles::             
* Input_from_binary_data_files::  
* New_plot_elements::           
* String_handling::             
* Macros::                      
* Auto-layout_of_multiple_plots_on_a_page::  
* Internal_variables::          
* New_or_revised_terminal_drivers::  
* Canvas_size::                 
@end menu

@node New_plot_styles, Input_from_binary_data_files, New_features_introduced_in_version_4.2, New_features_introduced_in_version_4.2
@subsection New plot styles



@menu
* Histogram::                   
* Label_plots::                 
* Image_data::                  
* Filled_curves::               
* Vectors::                     
@end menu

@node Histogram, Label_plots, New_plot_styles, New_plot_styles
@subsubsection Histogram

Histograms, or bar charts, can be produced.
See `histograms`.


@node Label_plots, Image_data, Histogram, New_plot_styles
@subsubsection Label plots

In coordination with the new `datastrings` feature described below, gnuplot
can draw a label at each vertex of a curve.
See `labels`.


@node Image_data, Filled_curves, Label_plots, New_plot_styles
@subsubsection Image data

The `image` and `rgbimage` styles allow to plot 2D images (from ascii or
`binary` files) and map them in a 2D or 3D plot.
See `image` and `rgbimage`.


@node Filled_curves, Vectors, Image_data, New_plot_styles
@subsubsection Filled curves

The plot style `fillstyle` has been augmented to allow to fill the area
between two input curves with a color or a pattern.
See `filledcurves`.


@node Vectors,  , Filled_curves, New_plot_styles
@subsubsection Vectors

Gnuplot can draw plots with vectors with a small arrowhead, requiring four or
six columns of data for 2D or 3D, respectively.
See `vectors`.


@node Input_from_binary_data_files, New_plot_elements, New_plot_styles, New_features_introduced_in_version_4.2
@subsection Input from binary data files

Gnuplot can now read a generic `binary` input, including matrix binary and
`general binary` (until now gnuplot supported only its own `binary matrix`
format). Several matrix file formats are autodetected (`gpbin`, `edf`, `avs`).
Binary data files are mainly useful for `image` and `rgbimage` drawings.
See `binary` and `binary general filetype`.


@node New_plot_elements, String_handling, Input_from_binary_data_files, New_features_introduced_in_version_4.2
@subsection New plot elements



@menu
* RGB_colors::                  
* Arbitrary_rectangles::        
@end menu

@node RGB_colors, Arbitrary_rectangles, New_plot_elements, New_plot_elements
@subsubsection RGB colors

Explicit RGB colors can be specified for all plot elements instead of
specifying a predefined linetype.
See @ref{colorspec}.


@node Arbitrary_rectangles,  , RGB_colors, New_plot_elements
@subsubsection Arbitrary rectangles

You can place rectangles with desired fill style and border anywhere in a 2D
plot.
See `set object rectangle`.


@node String_handling, Macros, New_plot_elements, New_features_introduced_in_version_4.2
@subsection String handling


@menu
* String_and_text_data_read_from_datafiles::  
* User-defined_string_variables::  
@end menu

@node String_and_text_data_read_from_datafiles, User-defined_string_variables, String_handling, String_handling
@subsubsection String and text data read from datafiles

Gnuplot can now read and process text fields in datafiles.
See `datastrings`.

@node User-defined_string_variables,  , String_and_text_data_read_from_datafiles, String_handling
@subsubsection User-defined string variables, operators, and functions

String variables and string functions are introduced. Most gnuplot commands
that previously required a string constant will now also accept a string
variable, a string expression, or a function that returns a string.
See @ref{variables}.


@node Macros, Auto-layout_of_multiple_plots_on_a_page, String_handling, New_features_introduced_in_version_4.2
@subsection Macros

Gnuplot supports command line macro expansion  by '@@stringvariablename'.
See @ref{macros}.


@node Auto-layout_of_multiple_plots_on_a_page, Internal_variables, Macros, New_features_introduced_in_version_4.2
@subsection Auto-layout of multiple plots on a page

The @ref{multiplot} mode is now able to layout automatically simple
multiplots without having to set the size or the position for each plot.
See @ref{multiplot}.


@node Internal_variables, New_or_revised_terminal_drivers, Auto-layout_of_multiple_plots_on_a_page, New_features_introduced_in_version_4.2
@subsection Internal variables

Gnuplot now exports several "read-only" variables such as GPVAL_TERM,
GPVAL_X_MIN, etc.
See @ref{variables}.


@node New_or_revised_terminal_drivers, Canvas_size, Internal_variables, New_features_introduced_in_version_4.2
@subsection New or revised terminal drivers


@menu
* `wxt`::                       
* `emf`::                       
* `gif`::                       
* @ref{postscript}::            
* `ai`::                        
* `epslatex`::                  
* `windows`::                   
@end menu

@node `wxt`, `emf`, New_or_revised_terminal_drivers, New_or_revised_terminal_drivers
@subsubsection `wxt`

The `wxt` terminal is an interactive and cross-platform terminal for on-screen
rendering. It uses the wxWidgets library for its user interface, and Cairo
associated with Pango for the actual rendering, providing nice plots with
antialiasing on lines and text. The terminal supports the full range of
gnuplot capabilities, including mousing, pm3d plots, image plots and
enhanced text.

@node `emf`, `gif`, `wxt`, New_or_revised_terminal_drivers
@subsubsection `emf`

The `emf` terminal generates an Enhanced Metafile Format file. This file
format is the metafile standard on MS Win32 Systems. The emf terminal
supports pm3d, rgb color, and image plot modes.

@node `gif`, @ref{postscript}, `emf`, New_or_revised_terminal_drivers
@subsubsection `gif`, `jpeg`, `png`

The code for the terminals using the `gd` library has been consolidated.
The `gif` terminal also knows how to produce an animated gif from a sequence
of plots.

@node @ref{postscript}, `ai`, `gif`, New_or_revised_terminal_drivers
@subsubsection @ref{postscript}

The @ref{postscript} terminal can load prologue files, which can contain
additional user-defined sections with, for example, character encodings.
See `postscript prologue`.

@node `ai`, `epslatex`, @ref{postscript}, New_or_revised_terminal_drivers
@subsubsection `ai`

The Adobe Illustrator `ai` driver is outdated. Since Adobe Illustrator
understands PostScript files, `set terminal post level1 ...` should be used
instead.

@node `epslatex`, `windows`, `ai`, New_or_revised_terminal_drivers
@subsubsection `epslatex`, `pslatex`, `pstex`

The terminals supporting an output to latex augmented by PostScript commands
have been consolidated. Many options are the same as in the @ref{postscript}
terminal.

@node `windows`,  , `epslatex`, New_or_revised_terminal_drivers
@subsubsection `windows`

The `windows` terminal now supports the `enhanced text` mode.


@node Canvas_size,  , New_or_revised_terminal_drivers, New_features_introduced_in_version_4.2
@subsection Canvas size

@c ?canvas size
@cindex canvas

@c ?set term size

In earlier versions of gnuplot, some terminal types used the values from
@ref{size} to control also the size of the output canvas; others did not.
The use of 'set size' for this purpose was deprecated in version 4.2.
In version 4.3 almost all terminals now behave as follows:

`set term <terminal_type> size <XX>, <YY>` controls the size of the output
file, or "canvas". Please see individual terminal documentation for allowed
values of the size parameters.  By default, the plot will fill this canvas.

`set size <XX>, <YY>` scales the plot itself relative to the size of the
canvas.  Scale values less than 1 will cause the plot to not fill the entire
canvas.  Scale values larger than 1 will cause only a portion of the plot to
fit on the canvas.  Please be aware that setting scale values larger than 1
may cause problems on some terminal types.

The major exception to this convention is the PostScript driver, which
by default continues to act as it has in earlier versions. Be warned that
the next version of gnuplot may change the default behaviour of the
PostScript driver as well.

Example:

@example
      set size 0.5, 0.5
      set term png size 600, 400
      set output "figure.png"
      plot "data" with lines

@end example

These commands will produce an output file "figure.png" that is 600 pixels
wide and 400 pixels tall. The plot will fill the lower left quarter of this
canvas.  This is consistent with the way multiplot mode has always worked,
however it is a change in the way the png driver worked for single plots in
version 4.0.


@node Backwards_compatibility, Features_introduced_in_version_4.0, New_features_introduced_in_version_4.2, gnuplot
@section Backwards compatibility

@c ?backwards compatibility
@cindex compatibility

Gnuplot version 4.0 deprecated certain syntax used in earlier versions, but
continued to recognize it.  This is now under the control of a configuration
option, and can be disabled as follows:

@example
      ./configure --disable-backwards-compatibility

@end example

Notice: Deprecated syntax items may be disabled permanently in some future
version of gnuplot.

One major difference is the introduction of keywords to disambiguate complex
commands, particularly commands containing string variables. A notable issue
was the use of bare numbers to specify offsets, line and point types.
Illustrative examples:

Deprecated:
@example
      set title "Old" 0,-1
      set data linespoints
      plot 1 2 4               # horizontal line at y=1
@end example

New:
@example
      TITLE = "New"
      set title TITLE offset char 0, char -1
      set style data linespoints
      plot 1 linetype 2 pointtype 4

@end example

Another compatibility issue is the effect of the command @ref{size} outside
when not in multiplot mode.  In earlier versions, the command
`set size <xx>, <yy>` caused some terminals to change both the size of the plot
and the size of the canvas is was drawn on; other terminatls changed only the
plot size.  The use of @ref{size} to change the canvas size is now deprecated.

Please see @ref{size}, @ref{size} and also the documentation for
individual terminals.


@node Features_introduced_in_version_4.0, Batch/Interactive_Operation, Backwards_compatibility, gnuplot
@section Features introduced in version 4.0

@c ?version 4 features
Gnuplot version 4.0 contained many features introduced since the preceding
official version 3.7.  These are summarized here.


@menu
* Mouse_and_hotkey_support_in_interactive_terminals::  
* New_terminals::               
* New_plot_style_@ref{pm3d}::   
* Filled_boxes::                
* New_plot_option_smooth_frequency::  
* Improved_text_options::       
* More_text_encodings::         
* Arrows::                      
* Data_file_format::            
* New_commands::                
* Other_changes_and_additions::  
* Accompanying_documentation::  
@end menu

@node Mouse_and_hotkey_support_in_interactive_terminals, New_terminals, Features_introduced_in_version_4.0, Features_introduced_in_version_4.0
@subsection Mouse and hotkey support in interactive terminals


Interaction with the current plot via mouse and hotkeys is supported for the
X11, OS/2 Presentation Manager, ggi, Windows, and wxWidgets terminals. See
`mouse input` for more information on mousing. See help for @ref{bind} for
information on hotkeys. Also see the documentation for individual mousing
terminals `ggi`, `pm`, `windows`, `wxt` and `x11`.

Sample script: mousevariables.dem


@node New_terminals, New_plot_style_@ref{pm3d}, Mouse_and_hotkey_support_in_interactive_terminals, Features_introduced_in_version_4.0
@subsection New terminals


`aqua`: New terminal for Mac OS X. Requires AquaTerm 1.0 or later.

`epslatex`: New terminal. Prepares eps figures for inclusion in LaTeX
documents.

`gif`: Consolidated with png/jpeg terminals. Requires libgd.

`ggi`: New full-screen interactive terminal for Linux. Interface to the
General Graphics Interface Library.

`pdf`: New terminal exporting Adobe Portable Document Format. Requires libpdf.

`png` and `jpeg`: Support for GIF, PNG and JPEG image output is provided by a
new driver via libgd. The new driver supports many more features than the
old png driver, including TrueType fonts. Requires libgd.

`svg`: New terminal exporting Scalable Vector Graphics.


@node New_plot_style_@ref{pm3d}, Filled_boxes, New_terminals, Features_introduced_in_version_4.0
@subsection New plot style @ref{pm3d}


The `splot` command is now capable of plotting 2D maps and 3D surfaces
colored by greyscale or color palettes. See help for @ref{pm3d}, @ref{palette},
@ref{cbrange}, `set view map`, `set colorbox` and @ref{palette}.

Sample scripts: pm3d.dem pm3dcolors.dem pm3dgamma.dem


@node Filled_boxes, New_plot_option_smooth_frequency, New_plot_style_@ref{pm3d}, Features_introduced_in_version_4.0
@subsection Filled boxes


A solid color or patterned fill style can be set for any plot style that
contains boxes. See `boxes`, `boxerrorbars`, `boxxyerrorbars`,
`candlesticks`, `set style fill`.

Sample scripts: fillstyle.dem candlesticks.dem


@node New_plot_option_smooth_frequency, Improved_text_options, Filled_boxes, Features_introduced_in_version_4.0
@subsection New plot option smooth frequency


Input data can be filtered through several built-in routines for interpolation
or approximation of data.  See @ref{smooth}, `frequency`, `unique`.

Sample scripts: steps.dem mgr.dem


@node Improved_text_options, More_text_encodings, New_plot_option_smooth_frequency, Features_introduced_in_version_4.0
@subsection Improved text options


Most gnuplot plot commands that produce text labels now accept modifiers to
specify text color, font, size, and rotation angle. See @ref{label}.
Not all terminal types support these options, however.  The enhanced text
mode previously available for the postscript and pm terminals has been
extended to other terminal types as well.  Terminal types currently supported
include aqua, dumb, jpeg, pdf, pm, png, postscript, x11, windows, and wxt.
See `enhanced text`.

Sample scripts: textcolor.dem textrotate.dem


@node More_text_encodings, Arrows, Improved_text_options, Features_introduced_in_version_4.0
@subsection More text encodings


Several terminals, including @ref{postscript}, `x11` and `pm`, support additional
text `encodings`: ISO 8859-1 (Latin 1), ISO 8859-2 (Latin 2), ISO 8859-15
(variant of 8859-1 with Euro sign), KOI8-R and KOI8-U (cyrillic), and
miscellaneous codepages. See @ref{encoding} for more details.


@node Arrows, Data_file_format, More_text_encodings, Features_introduced_in_version_4.0
@subsection Arrows


Single- or double-ended arrows can be placed on a plot individually from the
command line or from a data file via the `plot with vectors` style.
See @ref{arrow}, `plotting styles vectors`.

Sample scripts: arrowstyle.dem vector.dem


@node Data_file_format, New_commands, Arrows, Features_introduced_in_version_4.0
@subsection Data file format


The new @ref{datafile} command can be used to specify information about the
format of input data files, including the characters used to separate fields,
to indicate comment lines, and to specify missing data.  Gnuplot now attempts
to recognize text fields with embedded blanks as single entities based on the
datafile format settings.  This allows input from csv (comma-separated value)
files such as those exported by spreadsheet programs. See @ref{datafile}.
See also the `binary` option (introduced in 4.2).


@node New_commands, Other_changes_and_additions, Data_file_format, Features_introduced_in_version_4.0
@subsection New commands


`set view map` selects a top-view 2D projection of 3D surface plot.

`set term push` and `set term pop` save and restore the current terminal type.

`load` and @ref{save} commands accept piped input and output, respectively.


@node Other_changes_and_additions, Accompanying_documentation, New_commands, Features_introduced_in_version_4.0
@subsection Other changes and additions


Since gnuplot 4.0, `unset <something>` is preferred to `set no<something>`.
The older form has been deprecated.
Version 4.2 continues to allow the older syntax, but such backwards
compatibility may be lost in future versions.

Commands of the form `set <something> <style>` also are deprecated in favor
of the more general form `set style <something> <options>`.  Many more plot
elements now have style options of their own, including arrows, filled
areas, lines, and points. There are also style settings for input data and
formatting. Please see @ref{style}, @ref{decimalsign}, and @ref{datafile}.

The MS Windows package includes an additional executable `pgnuplot.exe` to
support piping command through standard input, which is otherwise not
available for graphical applications on this system.


@node Accompanying_documentation,  , Other_changes_and_additions, Features_introduced_in_version_4.0
@subsection Accompanying documentation


In directory docs/psdocs/ you may find new information in the gnuplot output
postscript file guide, list of postscript symbols in different encodings.

Improved FAQ. Please read it before asking your question in a public forum.

There are plenty of new demos *.dem in the demo/ directory. Please run them,
for example by
@example
      load "all.dem"
@end example

before asking for help.  Plots produced by the demo scripts can also be viewed
at
@uref{http://www.gnuplot.info/demo/,http://www.gnuplot.info/demo/
}


@node Batch/Interactive_Operation, Command-line-editing, Features_introduced_in_version_4.0, gnuplot
@section Batch/Interactive Operation

@cindex batch/interactive

`gnuplot` may be executed in either batch or interactive modes, and the two
may even be mixed together on many systems.

Any command-line arguments are assumed to be names of files containing
`gnuplot` commands (with the exception of standard X11 arguments, which are
processed first).  Each file is loaded with the `load` command, in the order
specified.  `gnuplot` exits after the last file is processed.  When no load
files are named, `gnuplot` enters into an interactive mode.  The special
filename "-" is used to denote standard input.

Both the @ref{exit} and @ref{quit} commands terminate the current command file and
`load` the next one, until all have been processed.

Examples:

To launch an interactive session:
@example
      gnuplot

@end example

To launch a batch session using two command files "input1" and "input2":
@example
      gnuplot input1 input2

@end example

To launch an interactive session after an initialization file "header" and
followed by another command file "trailer":
@example
      gnuplot header - trailer

@end example

@node Command-line-editing, Comments, Batch/Interactive_Operation, gnuplot
@section Command-line-editing

@cindex line-editing

@cindex editing

@cindex command-line-editing

Command-line editing is supported by the Unix, Atari, VMS, MS-DOS and OS/2
versions of `gnuplot`.  Also, a history mechanism allows previous commands to
be edited and re-executed.  After the command line has been edited, a newline
or carriage return will enter the entire line without regard to where the
cursor is positioned.

(The readline function in `gnuplot` is not the same as the readline used in
GNU Bash and GNU Emacs.  If the GNU version is desired, it may be selected
instead of the `gnuplot` version at compile time.)


The editing commands are as follows:


@example
      `Line-editing`:

@end example

@example
      ^B    moves back a single character.
      ^F    moves forward a single character.
      ^A    moves to the beginning of the line.
      ^E    moves to the end of the line.
      ^H    and DEL delete the previous character.
      ^D    deletes the current character.
      ^K    deletes from current position to the end of line.
      ^L,^R redraws line in case it gets trashed.
      ^U    deletes the entire line.
      ^W    deletes from the current word to the end of line.

@end example

@example
      `History`:

@end example

@example
      ^P    moves back through history.
      ^N    moves forward through history.

@end example


On the IBM PC, the use of a TSR program such as DOSEDIT or CED may be desired
for line editing.  The default makefile assumes that this is the case;  by
default `gnuplot` will be compiled with no line-editing capability.  If you
want to use `gnuplot`'s line editing, set READLINE in the makefile and add
readline.obj to the link file.  The following arrow keys may be used on the
IBM PC and Atari versions if readline is used:


@example
      Left  Arrow      - same as ^B.
      Right Arrow      - same as ^F.
      Ctrl Left  Arrow - same as ^A.
      Ctrl Right Arrow - same as ^E.
      Up    Arrow      - same as ^P.
      Down  Arrow      - same as ^N.

@end example


The Atari version of readline defines some additional key aliases:


@example
      Undo            - same as ^L.
      Home            - same as ^A.
      Ctrl Home       - same as ^E.
      Esc             - same as ^U.
      Help            - @ref{help} plus return.
      Ctrl Help       - @ref{help}.

@end example


@node Comments, Coordinates, Command-line-editing, gnuplot
@section Comments

@cindex comments

Comments are supported as follows: a `#` may appear in most places in a line
and `gnuplot` will ignore the rest of the line.  It will not have this effect
inside quotes, inside numbers (including complex numbers), inside command
substitutions, etc.  In short, it works anywhere it makes sense to work.

See also `set datafile commentschars` for specifying comment characters in
data files.

@node Coordinates, Datastrings, Comments, gnuplot
@section Coordinates

@cindex coordinates

The commands @ref{arrow}, @ref{key}, @ref{label} and @ref{object} allow you
to draw something at an arbitrary position on the graph.  This position is
specified by the syntax:

@example
      @{<system>@} <x>, @{<system>@} <y> @{,@{<system>@} <z>@}

@end example

Each <system> can either be `first`, `second`, `graph`, `screen`, or
`character`.

`first` places the x, y, or z coordinate in the system defined by the left
and bottom axes; `second` places it in the system defined by the second axes
(top and right); `graph` specifies the area within the axes---0,0 is bottom
left and 1,1 is top right (for splot, 0,0,0 is bottom left of plotting area;
use negative z to get to the base---see @ref{ticslevel}); `screen`
specifies the screen area (the entire area---not just the portion selected by
@ref{size}), with 0,0 at bottom left and 1,1 at top right; and `character`
gives the position in character widths and heights from the bottom left of
the screen area (screen 0,0), `character` coordinates depend on the chosen
font size.

If the coordinate system for x is not specified, `first` is used.  If the
system for y is not specified, the one used for x is adopted.

In some cases, the given coordinate is not an absolute position but a
relative value (e.g., the second position in @ref{arrow} ... `rto`).  In
most cases, the given value serves as difference to the first position.
If the given coordinate resides in a logarithmic axis the value is
interpreted as factor. For example,

@example
      set logscale x
      set arrow 100,5 rto 10,2

@end example

plots an arrow from position 100,5 to position 1000,7 since the x axis is
logarithmic while the y axis is linear.

If one (or more) axis is timeseries, the appropriate coordinate should
be given as a quoted time string according to the @ref{timefmt} format string.
See @ref{xdata} and @ref{timefmt}.  `gnuplot` will also accept an integer
expression, which will be interpreted as seconds from 1 January 2000.

@node Datastrings, Environment, Coordinates, gnuplot
@section Datastrings

@cindex datastrings

The configuration option --enable-datastrings allows gnuplot to read and
process text fields in datafiles. A text field consists of either an arbitrary
string of printable characters containing no whitespace or an arbitrary string
of characters, possibly including whitespace, delimited by double quotes.
The following sample line from a datafile is interpreted to contain four
columns, with a text field in column 3:

@example
  1.000 2.000 "Third column is all of this text" 4.00

@end example

Text fields can be positioned within a 2-D or 3-D plot using the commands:

@example
  plot 'datafile' using 1:2:4 with labels
  splot 'datafile using 1:2:3:4 with labels

@end example

A column of text data can also be used to label the ticmarks along one or more
of the plot axes. The example below plots a line through a series of points
with (X,Y) coordinates taken from columns 3 and 4 of the input datafile.
However, rather than generating regularly spaced tics along the x axis
labeled numerically, gnuplot will position a tic mark along the x axis at the
X coordinate of each point and label the tic mark with text taken from column
1 of the input datafile.

@example
  set xtics
  plot 'datafile' using 3:4:xticlabels(1) with linespoints

@end example

There is also an option that will interpret the first entry in a column of
input data as a text field, and use it as the key title for data plotted from
that column. The example given below will use the first entry in column 2 to
generate a title in the key box, while processing the remainder of columns
2 and 4 to draw the required line:

@example
  plot 'datafile' using 1:(f($2)/$4) title 2 with lines

@end example

See `set style labels`, `using xticlabels`, @ref{title}, @ref{using}.

@node Environment, Expressions, Datastrings, gnuplot
@section Environment

@cindex environment

A number of shell environment variables are understood by `gnuplot`.  None of
these are required, but may be useful.

If GNUTERM is defined, it is used as the name of the terminal type to be
used.  This overrides any terminal type sensed by `gnuplot` on start-up, but
is itself overridden by the .gnuplot (or equivalent) start-up file
(see `start-up`) and, of course, by later explicit changes.

On Unix, AmigaOS, AtariTOS, MS-DOS and OS/2, GNUHELP may be defined to be the
pathname of the HELP file (gnuplot.gih).

On VMS, the logical name GNUPLOT$HELP should be defined as the name of the
help library for `gnuplot`.  The `gnuplot` help can be put inside any system
help library, allowing access to help from both within and outside `gnuplot`
if desired.

On Unix, HOME is used as the name of a directory to search for a .gnuplot
file if none is found in the current directory.  On AmigaOS, AtariTOS,
MS-DOS, Windows and OS/2, GNUPLOT is used.  On Windows, the NT-specific
variable USERPROFILE is tried, too. VMS, SYS$LOGIN: is used. Type `help
start-up`.

On Unix, PAGER is used as an output filter for help messages.

On Unix, AtariTOS and AmigaOS, SHELL is used for the @ref{shell} command.  On
MS-DOS and OS/2, COMSPEC is used for the @ref{shell} command.

On MS-DOS, if the BGI or Watcom interface is used, PCTRM is used to tell
the maximum resolution supported by your monitor by setting it to
S<max. horizontal resolution>. E.g. if your monitor's maximum resolution is
800x600, then use:
@example
      set PCTRM=S800
@end example

If PCTRM is not set, standard VGA is used.

FIT_SCRIPT may be used to specify a `gnuplot` command to be executed when a
fit is interrupted---see @ref{fit}.  FIT_LOG specifies the default filename of the
logfile maintained by fit.

GNUPLOT_LIB may be used to define additional search directories for data
and command files. The variable may contain a single directory name, or
a list of directories separated by a platform-specific path separator,
eg. ':' on Unix, or ';' on DOS/Windows/OS/2/Amiga platforms. The contents
of GNUPLOT_LIB are appended to the @ref{loadpath} variable, but not saved
with the @ref{save} and `save set` commands.

Several gnuplot terminal drivers access TrueType fonts via the gd library.
For these drivers the font search path is controlled by the environmental
variable GDFONTPATH.  Furthermore, a default font for these drivers may be
set via the environmental variable GNUPLOT_DEFAULT_GDFONT.

The postscript terminal uses its own font search path. It is controlled by
the environmental variable GNUPLOT_FONTPATH. The format is the same as for
GNUPLOT_LIB. The contents of GNUPLOT_FONTPATH are appended to the @ref{fontpath}
variable, but not saved with the @ref{save} and `save set` commands.

GNUPLOT_PS_DIR is used by the postscript driver to use external prologue
files. Depending on the build process, gnuplot contains either a builtin
copy of those files or simply a default hardcoded path. Use this variable
to test the postscript terminal with custom prologue files. See
`postscript prologue`.

@node Expressions, Glossary, Environment, gnuplot
@section Expressions

@cindex expressions

In general, any mathematical expression accepted by C, FORTRAN, Pascal, or
BASIC is valid.  The precedence of these operators is determined by the
specifications of the C programming language.  White space (spaces and tabs)
is ignored inside expressions.

Complex constants are expressed as @{<real>,<imag>@}, where <real> and <imag>
must be numerical constants.  For example, @{3,2@} represents 3 + 2i; @{0,1@}
represents 'i' itself.  The curly braces are explicitly required here.

Note that gnuplot uses both "real" and "integer" arithmetic, like FORTRAN and
C.  Integers are entered as "1", "-10", etc; reals as "1.0", "-10.0", "1e1",
3.5e-1, etc.  The most important difference between the two forms is in
division: division of integers truncates: 5/2 = 2; division of reals does
not: 5.0/2.0 = 2.5.  In mixed expressions, integers are "promoted" to reals
before evaluation: 5/2e0 = 2.5.  The result of division of a negative integer
by a positive one may vary among compilers.  Try a test like "print -5/2" to
determine if your system chooses -2 or -3 as the answer.

The integer expression "1/0" may be used to generate an "undefined" flag,
which causes a point to ignored; the `ternary` operator gives an example.
Or you can use the pre-defined variable NaN to achieve the same result.
@cindex NaN


The real and imaginary parts of complex expressions are always real, whatever
the form in which they are entered: in @{3,2@} the "3" and "2" are reals, not
integers.

Gnuplot can also perform simple operations on strings and string variables.
For example, the expression ("A" . "B" eq "AB") evaluates as true, illustrating
the string concatenation operator and the string equality operator.

A string which contains a numerical value is promoted to the corresponding
integer or real value if used in a numerical expression. Thus ("3" + "4" == 7)
and (6.78 == "6.78") both evaluate to true.  An integer, but not a real or
complex value, is promoted to a string if used in string concatenation.
A typical case is the use of integers to construct file names or other strings;
e.g. ("file" . 4 eq "file4") is true.

Substrings can be specified using a postfixed range descriptor [beg:end].
For example, "ABCDEF"[3:4] == "CD"   and   "ABCDEF"[4:*] == "DEF"
The syntax "string"[beg:end] is exactly equivalent to calling the built-in
string-valued function substr("string",beg,end), except that you cannot
omit either beg or end from the function call.

@menu
* Functions::                   
* Operators::                   
* Gnuplot-defined_variables::   
* User-defined_variables_and_functions::  
@end menu

@node Functions, Operators, Expressions, Expressions
@subsection Functions

@c ?expressions functions
@cindex functions
@opindex functions


The functions in `gnuplot` are the same as the corresponding functions in
the Unix math library, except that all functions accept integer, real, and
complex arguments, unless otherwise noted.

For those functions that accept or return angles that may be given in either
degrees or radians (sin(x), cos(x), tan(x), asin(x), acos(x), atan(x),
atan2(x) and arg(z)), the unit may be selected by @ref{angles}, which
defaults to radians.



@menu
* abs::                         
* acos::                        
* acosh::                       
* arg::                         
* asin::                        
* asinh::                       
* atan::                        
* atan2::                       
* atanh::                       
* besj0::                       
* besj1::                       
* besy0::                       
* besy1::                       
* ceil::                        
* cos::                         
* cosh::                        
* erf::                         
* erfc::                        
* exp::                         
* floor::                       
* gamma::                       
* ibeta::                       
* inverf::                      
* igamma::                      
* imag::                        
* invnorm::                     
* int::                         
* lambertw::                    
* lgamma::                      
* log::                         
* log10::                       
* norm::                        
* rand::                        
* real::                        
* sgn::                         
* sin::                         
* sinh::                        
* sqrt::                        
* tan::                         
* tanh::                        
* gprintf::                     
* sprintf::                     
* strlen::                      
* strstrt::                     
* substr::                      
* strftime::                    
* strptime::                    
* system::                      
* word::                        
* words::                       
* column::                      
* defined::                     
* exists::                      
* stringcolumn::                
* timecolumn::                  
* tm_hour::                     
* tm_mday::                     
* tm_min::                      
* tm_mon::                      
* tm_sec::                      
* tm_wday::                     
* tm_yday::                     
* tm_year::                     
* valid::                       
* Random_number_generator::     
@end menu

@node abs, acos, Functions, Functions
@subsubsection abs

@c ?expressions functions abs
@c ?functions abs
@cindex abs
@findex abs


The `abs(x)` function returns the absolute value of its argument.  The
returned value is of the same type as the argument.

For complex arguments, abs(x) is defined as the length of x in the complex
plane [i.e.,  sqrt(real(x)**2 + imag(x)**2) ].

@node acos, acosh, abs, Functions
@subsubsection acos

@c ?expressions functions acos
@c ?functions acos
@cindex acos
@findex acos


The `acos(x)` function returns the arc cosine (inverse cosine) of its
argument.  `acos` returns its argument in radians or degrees, as selected by
@ref{angles}.

@node acosh, arg, acos, Functions
@subsubsection acosh

@c ?expressions functions acosh
@c ?functions acosh
@cindex acosh
@findex acosh


The `acosh(x)` function returns the inverse hyperbolic cosine of its argument
in radians.

@node arg, asin, acosh, Functions
@subsubsection arg

@c ?expressions functions arg
@c ?functions arg
@cindex arg
@findex arg


The `arg(x)` function returns the phase of a complex number in radians or
degrees, as selected by @ref{angles}.

@node asin, asinh, arg, Functions
@subsubsection asin

@c ?expressions functions asin
@c ?functions asin
@cindex asin
@findex asin


The `asin(x)` function returns the arc sin (inverse sin) of its argument.
`asin` returns its argument in radians or degrees, as selected by @ref{angles}.

@node asinh, atan, asin, Functions
@subsubsection asinh

@c ?expressions functions asinh
@c ?functions asinh
@cindex asinh
@findex asinh


The `asinh(x)` function returns the inverse hyperbolic sin of its argument in
radians.

@node atan, atan2, asinh, Functions
@subsubsection atan

@c ?expressions functions atan
@c ?functions atan
@cindex atan
@findex atan


The `atan(x)` function returns the arc tangent (inverse tangent) of its
argument.  `atan` returns its argument in radians or degrees, as selected by
@ref{angles}.

@node atan2, atanh, atan, Functions
@subsubsection atan2

@c ?expressions functions atan2
@c ?functions atan2
@cindex atan2
@findex atan2


The `atan2(y,x)` function returns the arc tangent (inverse tangent) of the
ratio of the real parts of its arguments.  @ref{atan2} returns its argument in
radians or degrees, as selected by @ref{angles}, in the correct quadrant.

@node atanh, besj0, atan2, Functions
@subsubsection atanh

@c ?expressions functions atanh
@c ?functions atanh
@cindex atanh
@findex atanh


The `atanh(x)` function returns the inverse hyperbolic tangent of its
argument in radians.

@node besj0, besj1, atanh, Functions
@subsubsection besj0

@c ?expressions functions besj0
@c ?functions besj0
@cindex besj0
@findex besj0


The `besj0(x)` function returns the j0th Bessel function of its argument.
@ref{besj0} expects its argument to be in radians.

@node besj1, besy0, besj0, Functions
@subsubsection besj1

@c ?expressions functions besj1
@c ?functions besj1
@cindex besj1
@findex besj1


The `besj1(x)` function returns the j1st Bessel function of its argument.
@ref{besj1} expects its argument to be in radians.

@node besy0, besy1, besj1, Functions
@subsubsection besy0

@c ?expressions functions besy0
@c ?functions besy0
@cindex besy0
@findex besy0


The `besy0(x)` function returns the y0th Bessel function of its argument.
@ref{besy0} expects its argument to be in radians.

@node besy1, ceil, besy0, Functions
@subsubsection besy1

@c ?expressions functions besy1
@c ?functions besy1
@cindex besy1
@findex besy1


The `besy1(x)` function returns the y1st Bessel function of its argument.
@ref{besy1} expects its argument to be in radians.

@node ceil, cos, besy1, Functions
@subsubsection ceil

@c ?expressions functions ceil
@c ?functions ceil
@cindex ceil
@findex ceil


The `ceil(x)` function returns the smallest integer that is not less than its
argument.  For complex numbers, @ref{ceil} returns the smallest integer not less
than the real part of its argument.

@node cos, cosh, ceil, Functions
@subsubsection cos

@c ?expressions functions cos
@c ?functions cos
@cindex cos
@findex cos


The `cos(x)` function returns the cosine of its argument.  `cos` accepts its
argument in radians or degrees, as selected by @ref{angles}.

@node cosh, erf, cos, Functions
@subsubsection cosh

@c ?expressions functions cosh
@c ?functions cosh
@cindex cosh
@findex cosh


The `cosh(x)` function returns the hyperbolic cosine of its argument.  @ref{cosh}
expects its argument to be in radians.

@node erf, erfc, cosh, Functions
@subsubsection erf

@c ?expressions functions erf
@c ?functions erf
@cindex erf
@findex erf


The `erf(x)` function returns the error function of the real part of its
argument.  If the argument is a complex value, the imaginary component is
ignored.  See @ref{erfc}, @ref{inverf}, and @ref{norm}.

@node erfc, exp, erf, Functions
@subsubsection erfc

@c ?expressions functions erfc
@c ?functions erfc
@cindex erfc
@findex erfc


The `erfc(x)` function returns 1.0 - the error function of the real part of
its argument.  If the argument is a complex value, the imaginary component is
ignored.  See `erf`, @ref{inverf}, and @ref{norm}.

@node exp, floor, erfc, Functions
@subsubsection exp

@c ?expressions functions exp
@c ?functions exp
@cindex exp
@findex exp


The `exp(x)` function returns the exponential function of its argument (`e`
raised to the power of its argument).  On some implementations (notably
suns), exp(-x) returns undefined for very large x.  A user-defined function
like safe(x) = x<-100 ? 0 : exp(x) might prove useful in these cases.

@node floor, gamma, exp, Functions
@subsubsection floor

@c ?expressions functions floor
@c ?functions floor
@cindex floor
@findex floor


The `floor(x)` function returns the largest integer not greater than its
argument.  For complex numbers, @ref{floor} returns the largest integer not
greater than the real part of its argument.

@node gamma, ibeta, floor, Functions
@subsubsection gamma

@c ?expressions functions gamma
@c ?functions gamma
@cindex gamma
@findex gamma


The `gamma(x)` function returns the gamma function of the real part of its
argument.  For integer n, gamma(n+1) = n!.  If the argument is a complex
value, the imaginary component is ignored.

@node ibeta, inverf, gamma, Functions
@subsubsection ibeta

@c ?expressions functions ibeta
@c ?functions ibeta
@cindex ibeta
@findex ibeta


The `ibeta(p,q,x)` function returns the incomplete beta function of the real
parts of its arguments. p, q > 0 and x in [0:1].  If the arguments are
complex, the imaginary components are ignored.

@node inverf, igamma, ibeta, Functions
@subsubsection inverf

@c ?expressions functions inverf
@c ?functions inverf
@cindex inverf
@findex inverf


The `inverf(x)` function returns the inverse error function of the real part
of its argument.   See `erf` and @ref{invnorm}.

@node igamma, imag, inverf, Functions
@subsubsection igamma

@c ?expressions functions igamma
@c ?functions igamma
@cindex igamma
@findex igamma


The `igamma(a,x)` function returns the normalized incomplete gamma
function of the real parts of its arguments, where a > 0 and x >= 0.
The standard notation is P(a,x), e.g. Abramowitz and Stegun (6.5.1),
with limiting value of 1 as x approaches infinity.  If the arguments
are complex, the imaginary components are ignored.

@node imag, invnorm, igamma, Functions
@subsubsection imag

@c ?expressions functions imag
@c ?functions imag
@cindex imag
@findex imag


The `imag(x)` function returns the imaginary part of its argument as a real
number.

@node invnorm, int, imag, Functions
@subsubsection invnorm

@c ?expressions functions invnorm
@c ?functions invnorm
@cindex invnorm
@findex invnorm


The `invnorm(x)` function returns the inverse cumulative normal (Gaussian)
distribution function of the real part of its argument.  See @ref{norm}.

@node int, lambertw, invnorm, Functions
@subsubsection int

@c ?expressions functions int
@c ?functions int
@cindex int
@findex int


The `int(x)` function returns the integer part of its argument, truncated
toward zero.

@node lambertw, lgamma, int, Functions
@subsubsection lambertw

@c ?expressions functions lambertw
@c ?functions lambertw
@cindex lambertw
@findex lambertw


The lambertw function returns the value of the principal branch of
Lambert's W function, which is defined by the equation (W(z)*exp(W(z))=z.
z must be a real number with z >= -exp(-1).

@node lgamma, log, lambertw, Functions
@subsubsection lgamma

@c ?expressions functions lgamma
@c ?functions lgamma
@cindex lgamma
@findex lgamma


The `lgamma(x)` function returns the natural logarithm of the gamma function
of the real part of its argument.  If the argument is a complex value, the
imaginary component is ignored.

@node log, log10, lgamma, Functions
@subsubsection log

@c ?expressions functions log
@c ?functions log
@cindex log
@findex log


The `log(x)` function returns the natural logarithm (base `e`) of its
argument.  See @ref{log10}.

@node log10, norm, log, Functions
@subsubsection log10

@c ?expressions functions log10
@c ?functions log10
@cindex log10
@findex log10


The `log10(x)` function returns the logarithm (base 10) of its argument.

@node norm, rand, log10, Functions
@subsubsection norm

@c ?expressions functions norm
@c ?functions norm
@cindex norm
@findex norm


The `norm(x)` function returns the cumulative normal (Gaussian) distribution
function of the real part of its argument.   See @ref{invnorm}, `erf` and @ref{erfc}.

@node rand, real, norm, Functions
@subsubsection rand

@c ?expressions functions rand
@c ?functions rand
@cindex rand
@findex rand


`rand(0)`  returns a pseudo random number in the interval [0:1] generated
@example
           from the current value of two internal 32-bit seeds.
@end example

`rand(-1)` resets both seeds to a standard value.
`rand(x)`  for x>0 sets both seeds to a value based on the value of x.
`rand(@{x,y@})` for x>0 sets seed1 to x and seed2 to y.
Note: This behavior has changed starting with gnuplot version 3.8l. Older
scripts that expected rand(x>0) to produce sequential pseudo-random numbers
from the same seeded sequence must be changed to call rand(0) instead.

@node real, sgn, rand, Functions
@subsubsection real

@c ?expressions functions real
@c ?functions real
@cindex real
@findex real


The `real(x)` function returns the real part of its argument.

@node sgn, sin, real, Functions
@subsubsection sgn

@c ?expressions functions sgn
@c ?functions sgn
@cindex sgn
@findex sgn


The `sgn(x)` function returns 1 if its argument is positive, -1 if its
argument is negative, and 0 if its argument is 0.  If the argument is a
complex value, the imaginary component is ignored.

@node sin, sinh, sgn, Functions
@subsubsection sin

@c ?expressions functions sin
@c ?functions sin
@cindex sin
@findex sin


The `sin(x)` function returns the sine of its argument.  `sin` expects its
argument to be in radians or degrees, as selected by @ref{angles}.

@node sinh, sqrt, sin, Functions
@subsubsection sinh

@c ?expressions functions sinh
@c ?functions sinh
@cindex sinh
@findex sinh


The `sinh(x)` function returns the hyperbolic sine of its argument.  @ref{sinh}
expects its argument to be in radians.

@node sqrt, tan, sinh, Functions
@subsubsection sqrt

@c ?expressions functions sqrt
@c ?functions sqrt
@cindex sqrt
@findex sqrt


The `sqrt(x)` function returns the square root of its argument.

@node tan, tanh, sqrt, Functions
@subsubsection tan

@c ?expressions functions tan
@c ?functions tan
@cindex tan
@findex tan


The `tan(x)` function returns the tangent of its argument.  `tan` expects
its argument to be in radians or degrees, as selected by @ref{angles}.

@node tanh, gprintf, tan, Functions
@subsubsection tanh

@c ?expressions functions tanh
@c ?functions tanh
@cindex tanh
@findex tanh


The `tanh(x)` function returns the hyperbolic tangent of its argument.  @ref{tanh}
expects its argument to be in radians.




@node gprintf, sprintf, tanh, Functions
@subsubsection gprintf

@c ?expressions functions gprintf
@c ?functions gprintf
`gprintf("format",x)` applies gnuplot's own format specifiers to the single
variable x and returns the resulting string. If you want standard C-language
format specifiers, you must instead use `sprintf("format",x)`.
See `format specifiers`.

@node sprintf, strlen, gprintf, Functions
@subsubsection sprintf

@c ?expressions functions sprintf
@c ?functions sprintf
@cindex sprintf
@findex sprintf


`sprintf("format",var1,var2,...)` applies standard C-language format specifiers
to multiple arguments (10 max) and returns the resulting string. If you want to
use gnuplot's own format specifiers, you must instead call `gprintf()`.
For information on sprintf format specifiers, please see standard C-language
documentation or the unix sprintf man page.

@node strlen, strstrt, sprintf, Functions
@subsubsection strlen

@c ?expressions functions strlen
@c ?functions strlen
@cindex strlen
@findex strlen


`strlen("string")` returns the number of characters in the string.

@node strstrt, substr, strlen, Functions
@subsubsection strstrt

@c ?expressions functions strstrt
@c ?functions strstrt
@cindex strstrt
@findex strstrt


`strstrt("string","key")` searches for the character string "key" in "string"
and returns the index to the first character of "key". If "key" is not found,
returns 0. Similar to C library function strstr except that it returns an
index rather than a string pointer. strstrt("hayneedlestack","needle") = 4.

@node substr, strftime, strstrt, Functions
@subsubsection substr

@c ?expressions functions substr
@c ?functions substr
@cindex substr
@findex substr


@cindex substring

`substr("string",beg,end)` returns the substring consisting of characters
beg through end of the original string. This is exactly equivalent to the
expression "string"[beg:end] except that you do not have the option of
ommitting beg or end.

@node strftime, strptime, substr, Functions
@subsubsection strftime

@c ?expressions functions strftime
@c ?functions strftime
@cindex strftime
@findex strftime


`strftime("timeformat",t)` applies the timeformat specifiers to the time t
given in seconds since the year 2000. 
See `time_specifiers` and @ref{strptime}.

@node strptime, system, strftime, Functions
@subsubsection strptime

@c ? expressions functions strptime
@c ?functions strptime
@cindex strptime
@findex strptime


`strptime("timeformat",s)` reads the time from the string s using the
timeformat specifiers and converts it into seconds since the year 2000.
See `time_specifiers` and @ref{strftime}.

@node system, word, strptime, Functions
@subsubsection system

@c ?expressions functions system
@c ?functions system
@c ?system function
@cindex system
@cmindex system


`system("command")` executes "command" using the standard shell and returns
the resulting character stream from stdout as string variable.
One optional trailing newline is ignored.

This can be used to import external functions into gnuplot scripts using
'f(x) = real(system(sprintf("somecommand %f", x)))'.

@node word, words, system, Functions
@subsubsection word

@c ?expressions functions word
@c ?functions word
@cindex word
@findex word


@cindex word
@findex word


`word("string",n)` returns the nth word in string. For example,
`word("one two three",2)` returns the string "two".

@node words, column, word, Functions
@subsubsection words

@c ?expressions functions words
@c ?functions words
@cindex words
@findex words


@cindex words
@findex words


`words("string")` returns the number of words in string. For example,
`words(" a b c d")` returns the 4.




@node column, defined, words, Functions
@subsubsection column

@c ?expressions functions column
@c ?functions column
@cindex column
@findex column


`column(x)` may be used only in expressions as part of @ref{using} manipulations
to fits or datafile plots.  It evaluates to the numerical value of the contents
of column x. See @ref{using}.

@node defined, exists, column, Functions
@subsubsection defined

@c ?expressions functions defined
@c ?functions defined
@cindex defined
@findex defined


`defined(X)` [DEPRECATED] returns 1 if a variable named X has been defined, otherwise
it returns 0.

@node exists, stringcolumn, defined, Functions
@subsubsection exists

@c ?expressions functions exists
@c ?functions exists
@cindex exists
@findex exists


The argument to exists() is a string constant or a string variable;
if the string contains the name of a defined variable, the function returns 1.
Otherwise the function returns 0.

@node stringcolumn, timecolumn, exists, Functions
@subsubsection stringcolumn

@c ?expressions functions stringcolumn
@c ?functions stringcolumn
@cindex stringcolumn
@findex stringcolumn


@c ?expressions functions strcol
@c ?functions strcol
@cindex strcol

`stringcolumn(x)` may be used only in expressions as part of @ref{using} manipulations
to fits or datafile plots.  It returns the content of column x as a string variable.
See @ref{using}.

@node timecolumn, tm_hour, stringcolumn, Functions
@subsubsection timecolumn

@c ?expressions functions timecolumn
@c ?functions timecolumn
@cindex timecolumn
@findex timecolumn


`timecolumn(x)` may be used only in expressions as part of @ref{using}
manipulations to fits or datafile plots.   See @ref{using}.

It reads the data starting at that column as a time/date value and
returns its value in gnuplot's internal time representation of
"seconds since the millennium".

To find the right @ref{timefmt} string to use, @ref{timecolumn} searches for a
@ref{using} specification with the same column number as its argument.
If one is found, @ref{timefmt} pattern of the target axis for this specifier
is used.  Otherwise, @ref{timecolumn} chooses the x axis @ref{timefmt} per default.

@node tm_hour, tm_mday, timecolumn, Functions
@subsubsection tm_hour

@c ?expressions tm_hour
@findex tm_hour
@c ?functions tm_hour
@cindex tm_hour
@findex tm_hour


The @ref{tm_hour} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the hour (an integer in the range 0--23) as a real.

@node tm_mday, tm_min, tm_hour, Functions
@subsubsection tm_mday

@c ?expressions tm_mday
@findex tm_mday
@c ?functions tm_mday
@cindex tm_mday
@findex tm_mday


The @ref{tm_mday} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the day of the month (an integer in the range 1--31)
as a real.

@node tm_min, tm_mon, tm_mday, Functions
@subsubsection tm_min

@c ?expressions tm_min
@findex tm_min
@c ?functions tm_min
@cindex tm_min
@findex tm_min


The @ref{tm_min} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the minute (an integer in the range 0--59) as a real.

@node tm_mon, tm_sec, tm_min, Functions
@subsubsection tm_mon

@c ?expressions tm_mon
@findex tm_mon
@c ?functions tm_mon
@cindex tm_mon
@findex tm_mon


The @ref{tm_mon} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the month (an integer in the range 0--11) as a real.

@node tm_sec, tm_wday, tm_mon, Functions
@subsubsection tm_sec

@c ?expressions tm_sec
@findex tm_sec
@c ?functions tm_sec
@cindex tm_sec
@findex tm_sec


The @ref{tm_sec} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the second (an integer in the range 0--59) as a real.

@node tm_wday, tm_yday, tm_sec, Functions
@subsubsection tm_wday

@c ?expressions tm_wday
@findex tm_wday
@c ?functions tm_wday
@cindex tm_wday
@findex tm_wday


The @ref{tm_wday} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the day of the week (an integer in the range 0--6) as
a real.

@node tm_yday, tm_year, tm_wday, Functions
@subsubsection tm_yday

@c ?expressions tm_yday
@findex tm_yday
@c ?functions tm_yday
@cindex tm_yday
@findex tm_yday


The @ref{tm_yday} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the day of the year (an integer in the range 1--366)
as a real.

@node tm_year, valid, tm_yday, Functions
@subsubsection tm_year

@c ?expressions tm_year
@findex tm_year
@c ?functions tm_year
@cindex tm_year
@findex tm_year


The @ref{tm_year} function interprets its argument as a time, in seconds from
1 Jan 2000.  It returns the year (an integer) as a real.

@node valid, Random_number_generator, tm_year, Functions
@subsubsection valid

@c ?expressions functions valid
@c ?functions valid
@cindex valid
@findex valid


`valid(x)` may be used only in expressions as part of @ref{using} manipulations
to fits or datafile plots.  See @ref{using}.

See also
@uref{http://www.gnuplot.info/demo/airfoil.html,airfoil.dem: use of functions and complex variables for airfoils demo.
}


@node Random_number_generator,  , valid, Functions
@subsubsection Random number generator

@c ?expressions random
@c ?functions random
@cindex random

The behavior of the built-in function `rand(x)` has changed as of version 3.8l.
Older scripts that expected rand(x>0) to produce sequential pseudo-random
numbers from the same seeded sequence must be changed to call rand(0) instead.
The current behavior is as follows:
@example
 `rand(0)`  returns a pseudo random number in the interval [0:1] generated
            from the current value of two internal 32-bit seeds.
 `rand(-1)` resets both seeds to a standard value.
 `rand(x)`  for x>0 sets both seeds to a value based on the value of x.
 `rand(@{x,y@})` for x>0 sets seed1 to x and seed2 to y.

@end example


@node Operators, Gnuplot-defined_variables, Functions, Expressions
@subsection Operators

@c ?expressions operators
@cindex operators

The operators in `gnuplot` are the same as the corresponding operators in the
C programming language, except that all operators accept integer, real, and
complex arguments, unless otherwise noted.  The ** operator (exponentiation)
is supported, as in FORTRAN.

Parentheses may be used to change order of evaluation.

@menu
* Unary::                       
* Binary::                      
* Ternary::                     
@end menu

@node Unary, Binary, Operators, Operators
@subsubsection Unary

@c ?expressions operators unary
@c ?operators unary
@cindex unary

The following is a list of all the unary operators and their usages:


@example
    Symbol      Example    Explanation
      -           -a          unary minus
      +           +a          unary plus (no-operation)
      ~           ~a        * one's complement
      !           !a        * logical negation
      !           a!        * factorial
      $           $3        * call arg/column during @ref{using} manipulation
@end example

@cindex factorial

@cindex negation

@cindex one's complement

@cindex operator precedence


(*) Starred explanations indicate that the operator requires an integer
argument.

Operator precedence is the same as in Fortran and C.  As in those languages,
parentheses may be used to change the order of operation.  Thus -2**2 = -4,
but (-2)**2 = 4.

The factorial operator returns a real number to allow a greater range.

@node Binary, Ternary, Unary, Operators
@subsubsection Binary

@c ?expressions operators binary
@c ?operators binary
The following is a list of all the binary operators and their usages:


@example
    Symbol       Example      Explanation
      **          a**b          exponentiation
      *           a*b           multiplication
      /           a/b           division
      %           a%b         * modulo
      +           a+b           addition
      -           a-b           subtraction
      ==          a==b          equality
      !=          a!=b          inequality
      <           a<b           less than
      <=          a<=b          less than or equal to
      >           a>b           greater than
      >=          a>=b          greater than or equal to
      &           a&b         * bitwise AND
      ^           a^b         * bitwise exclusive OR
      |           a|b         * bitwise inclusive OR
      &&          a&&b        * logical AND
      ||          a||b        * logical OR
      .           A.B           string concatenation
      eq          A eq B        string equality
      ne          A ne B        string inequality
@end example

@cindex bitwise operators

@cindex string operators

@cindex modulo

@cindex exponentiation



(*) Starred explanations indicate that the operator requires integer
arguments.
Capital letters A and B indicate that the operator requires string arguments.

Logical AND (&&) and OR (||) short-circuit the way they do in C.  That is,
the second `&&` operand is not evaluated if the first is false; the second
`||` operand is not evaluated if the first is true.

@node Ternary,  , Binary, Operators
@subsubsection Ternary

@c ?expressions operators ternary
@c ?operators ternary
@cindex ternary

There is a single ternary operator:


@example
    Symbol       Example      Explanation
      ?:          a?b:c     ternary operation

@end example


The ternary operator behaves as it does in C.  The first argument (a), which
must be an integer, is evaluated.  If it is true (non-zero), the second
argument (b) is evaluated and returned; otherwise the third argument (c) is
evaluated and returned.

The ternary operator is very useful both in constructing piecewise functions
and in plotting points only when certain conditions are met.

Examples:

Plot a function that is to equal sin(x) for 0 <= x < 1, 1/x for 1 <= x < 2,
and undefined elsewhere:
@example
      f(x) = 0<=x && x<1 ? sin(x) : 1<=x && x<2 ? 1/x : 1/0
      plot f(x)
@end example

@c ^ <img align=bottom src="http://www.gnuplot.info/doc/ternary.gif" alt="[ternary.gif]" width=640 height=480>
Note that `gnuplot` quietly ignores undefined values, so the final branch of
the function (1/0) will produce no plottable points.  Note also that f(x)
will be plotted as a continuous function across the discontinuity if a line
style is used.  To plot it discontinuously, create separate functions for the
two pieces.  (Parametric functions are also useful for this purpose.)

For data in a file, plot the average of the data in columns 2 and 3 against
the datum in column 1, but only if the datum in column 4 is non-negative:

@example
      plot 'file' using 1:( $4<0 ? 1/0 : ($2+$3)/2 )

@end example

Please see @ref{using} for an explanation of the @ref{using} syntax.


@node Gnuplot-defined_variables, User-defined_variables_and_functions, Operators, Expressions
@subsection Gnuplot-defined variables

@c ?gnuplot-defined variables
The variable `pi` is defined to be pi, see
@example
      print pi

@end example

Additionally, gnuplot may define some variables under various operations.

Working with interactive terminals with `mouse` functionality defines
variables with names that begin "MOUSE_", see @ref{variables} for details.

Further, there are several "read-only" variables that begin "GPVAL_", like
GPVAL_TERM, GPVAL_X_MIN, GPVAL_X_MAX, GPVAL_Y_MIN,... Type `show variables all`
to display their list and values. Values related to axes parameters (ranges, log
base) are values used during the last plot, not those currently `set`.

The @ref{fit} mechanism uses several variables with names that begin "FIT_".  It
is safest to avoid using such names.  "FIT_LIMIT", however, is one that you
may wish to redefine. Under `set fit errorvariables`, the error for each
fitted parameter will be stored in a variable named like the parameter, but
with "_err" appended. See the documentation on @ref{fit} for details.

See @ref{variables}, @ref{variables}, and @ref{fit}.


@node User-defined_variables_and_functions,  , Gnuplot-defined_variables, Expressions
@subsection User-defined variables and functions

@c ?expressions user-defined
@c ?user-defined variables
@cindex user-defined

@cindex variables
@opindex variables


New user-defined variables and functions of one through five variables may
be declared and used anywhere, including on the `plot` command itself.

User-defined function syntax:
@example
      <func-name>( <dummy1> @{,<dummy2>@} ... @{,<dummy5>@} ) = <expression>

@end example

where <expression> is defined in terms of <dummy1> through <dummy5>.

User-defined variable syntax:
@example
      <variable-name> = <constant-expression>

@end example

Examples:
@example
      w = 2
      q = floor(tan(pi/2 - 0.1))
      f(x) = sin(w*x)
      sinc(x) = sin(pi*x)/(pi*x)
      delta(t) = (t == 0)
      ramp(t) = (t > 0) ? t : 0
      min(a,b) = (a < b) ? a : b
      comb(n,k) = n!/(k!*(n-k)!)
      len3d(x,y,z) = sqrt(x*x+y*y+z*z)
      plot f(x) = sin(x*a), a = 0.2, f(x), a = 0.4, f(x)

@end example

@example
      file = "mydata.inp"
      file(n) = sprintf("run_%d.dat",n)

@end example

@c ^ <img align=bottom src="http://www.gnuplot.info/doc/userdefined.gif" alt="[userdefined.gif]" width=640 height=480>
The final two examples illustrate a user-defined string variable and a
user-defined string function.

@cindex NaN

@cindex pi

Note that the variables `pi` (3.14159...) and `NaN` (IEEE "Not a Number") are
already defined.  You can redefine these to something else if you really need
to. The original values can be recovered by setting:

@example
      NaN = GPVAL_NaN
      pi  = GPVAL_pi

@end example

Other variables may be defined under various gnuplot operations like mousing in
interactive terminals or fitting; see @ref{variables} for details.

You can check for existence of a given variable V by the exists("V")
expression. For example
@example
      a = 10
      if (exists("a")) print "a is defined"
      if (!exists("b")) print "b is not defined"

@end example

Valid names are the same as in most programming languages: they must begin
with a letter, but subsequent characters may be letters, digits, "$", or "_".

See @ref{functions}, @ref{functions}, @ref{variables}, @ref{macros}.

@node Glossary, linetype, Expressions, gnuplot
@section Glossary

@cindex glossary

Throughout this document an attempt has been made to maintain consistency of
nomenclature.  This cannot be wholly successful because as `gnuplot` has
evolved over time, certain command and keyword names have been adopted that
preclude such perfection.  This section contains explanations of the way
some of these terms are used.

A "page" or "screen" is the entire area addressable by `gnuplot`.  On a
monitor, it is the full screen; on a plotter, it is a single sheet of paper.

A screen may contain one or more "plots".  A plot is defined by an abscissa
and an ordinate, although these need not actually appear on it, as well as
the margins and any text written therein.

A plot contains one "graph".  A graph is defined by an abscissa and an
ordinate, although these need not actually appear on it.

A graph may contain one or more "lines".  A line is a single function or
data set.  "Line" is also a plotting style.  The word will also be used in
sense "a line of text".  Presumably the context will remove any ambiguity.

The lines on a graph may have individual names.  These may be listed
together with a sample of the plotting style used to represent them in
the "key", sometimes also called the "legend".

The word "title" occurs with multiple meanings in `gnuplot`.  In this
document, it will always be preceded by the adjective "plot", "line", or
"key" to differentiate among them.

A 2-d graph may have up to four labelled axes.  The names of the four axes
for these usages are "x" for the axis along the bottom border of the plot,
"y" for the left border, "x2" for the top border, and "y2" for the right
border.

A 3-d graph may have up to three labelled axes -- "x", "y" and "z".  It is
not possible to say where on the graph any particular axis will fall because
you can change the direction from which the graph is seen with @ref{view}.

When discussing data files, the term "record" will be resurrected and used
to denote a single line of text in the file, that is, the characters between
newline or end-of-record characters.  A "point" is the datum extracted from
a single record.  A "datablock" is a set of points from consecutive records,
delimited by blank records.  A line, when referred to in the context of a
data file, is a subset of a datablock.

@node linetype, mouse_input, Glossary, gnuplot
@section linetype, colors, and styles

@cindex linetype

@cindex colors

Each gnuplot terminal type provides a set of distinct "linetypes". These may
differ in color, in thickness, in dot/dash pattern, or in some combination of
color and dot/dash. The default linetypes for a particular terminal can be
previewed by issuing the @ref{test} command after setting the terminal type.
The pre-defined colors and dot/dash patterns are not guaranteed to be
consistent for all terminal types, but all terminals use the special linetype
-1 to mean a solid line in the primary foreground color (normally black).
By default, successive functions or datafiles plotted by a single command will
be assigned successive linetypes.  You can override this default by specifying
a particular linetype for any function, datafile, or plot element.

Examples:

@example
     plot "foo", "bar"                 # plot two files using linetypes 1, 2
     plot sin(x) linetype 4            # terminal-specific linetype color 4
     plot sin(x) lt -1                 # black

@end example

@cindex colors

For many terminal types it is also possible to assign user-defined colors
using explicit rgb (red, green, blue) values, named colors, or color values
that refer to the current PM3D palette.

Examples:

@example
     plot sin(x) lt rgb "violet"       # one of gnuplot's named colors
     plot sin(x) lt rgb "#FF00FF"      # explicit RGB triple in hexadecimal
     plot sin(x) lt palette cb -45     # whatever color corresponds to -45
                                       # in the current cbrange of the palette
     plot sin(x) lt palette frac 0.3   # fractional value along the palette

@end example

See @ref{colornames}, @ref{palette}, @ref{cbrange}.

For terminals that support dot/dash patterns, each default linetype has both
a dot-dash pattern and a default color. However, you can override the default
color by using the keyword `linecolor`, abbreviated `lc`.  For example, the
postscript terminal provides a dashed blue line as linetype 3.  The plot
commands below use this same dash pattern for three plots, one in blue (the
default), another in red (the default for linetype 1), and a third in gold.

Example:

@example
     set term postscript dashed color
     plot 'foo' lt 3, 'baz' lt 3 linecolor 1, 'bar' lt 3 lc rgb 'gold'

@end example

Lines can have additional properties such as linewidth.  You can associate
these various properties, as well as equivalent properties for point symbols,
into user-defined "line styles" using the command `set style line`.  Once
you have defined a linestyle, you can use it in a plot command to control
the appearance of one or more plot elements.

Examples:

@example
     # define a new line style with terminal-independent color cyan,
     # linewidth 3, and associated point type 6 (a circle with a dot in it).
     set style line 5 lt rgb "cyan" lw 3 pt 6
     plot sin(x) with linespoints ls 5          # user-defined line style 5

@end example

See `linestyle`, `set style line`.

@menu
* colorspec::                   
@end menu

@node colorspec,  , linetype, linetype
@subsection colorspec

@cindex colorspec

@cindex rgbcolor

@cindex lc

@cindex linecolor

@cindex tc

@cindex textcolor

@cindex colors

Many commands allow you to specify a linetype with an explicit color.
Note that not all terminals support RGB colors or pm3d palette colors.

Syntax:

@example
      ... @{linetype | lt@} <colorspec>
      ... @{linecolor | lc@} <colorspec>
      ... @{textcolor | tc@} <colorspec>

@end example

where <colorspec> has one of the following forms:

@example
      rgbcolor "colorname"
      rgbcolor "#RRGGBB"
      rgbcolor variable
      palette frac <val>      # <val> runs from 0 to 1
      palette cb <value>      # <val> lies within cbrange
      palette z
      variable                # color index is read from input file

@end example

"colorname" refers to one of the color names built in to gnuplot. For a list
of the available names, see @ref{colornames}.

"#RRGGBB" is a hexadecimal constant preceded by the "#" symbol. The RRGGBB
represents the red, green, and blue components of the color, each on a scale
from 0 - 255.  For example, magenta = full-scale red + full-scale blue would
be represented by #FF00FF, which is the hexadecimal representation of
(255 << 16) + (0 << 8) + (255).

"rgb variable" requires an additional column in the @ref{using} specifier, and
is only available in 3D plotting mode (splot). The extra column is interpreted
as a 24-bit packed RGB triple. These are most easily specified in a data file
as hexadecimal values (see above).

Example:

@example
      rgb(r,g,b) = 65536 * int(r) + 256 * int(g) + int(b)
      splot "data" using 1:2:3:(rgb($1,$2,$3)) with points lc rgb variable

@end example

The color palette is a linear gradient of colors that smoothly maps a
single numerical value onto a particular color.  Two such mappings are always
in effect. `palette frac`  maps a fractional value between 0 and 1 onto the
full range of the color palette.  `palette cb` maps the range of the color
axis onto the same palette.  See @ref{cbrange}.  See also `set colorbox`.
You can use either of these to select a constant color from the current
palette.

"palette z" maps the z value of each plot segment or plot element into the
cbrange mapping of the palette. This allows smoothly-varying color along a
3D line or surface.  It also allows coloring 2D plots by palette values read
from an extra column of data.

@menu
* linecolor_variable::          
@end menu

@node linecolor_variable,  , colorspec, colorspec
@subsubsection linecolor variable

@c ?linecolor variable
@c ?lc variable
@c ?textcolor variable
@c ?tc variable
Most plot commands assign a single color (linetype) to each element of the
plot.  If there are multiple plots on a single graph, the default color
(linetype) is incremented sequentially.  You can instead assign a separate
color for each data point, line segment, or label based on additional 
information in the input data file.  This is indicated by the colorspec
keyword `variable`. 

`lc variable` tells the program to use the value read from one column of the
input data as a linestyle index, and use the color belonging to that linestyle.
This requires a corresponding additional column in the @ref{using} specifier.
Text colors can be set similarly using `tc variable`.

A single data file may contain multiple sets of data, separated by two blank
lines. Each of these separate sets is assigned an index value (see @ref{index})
that can be retrieved via the using specifier column(-2).
All data in the file is drawn with the same color/linestyle/pointtype
properties by default.  The command `lc variable` can be used to assign
different colors to each data set in the file by using the index value from
pseudocolumn -2.

Examples:
@example
      # Use the third column of data to assign colors to individual points
      plot 'data' using 1:2:3 with points lc variable

@end example

@example
      # Use the data set index to choose a linestyle color
      plot 'data' using 1:2:(column(-2)) with lines lc variable

@end example


@node mouse_input, Plotting, linetype, gnuplot
@section mouse input

@c ?mouse input
The `x11`, `pm`, `windows`, `ggi`, and `wxt` terminals allow interaction with
the current plot using the mouse. They also support the definition of hotkeys
to activate pre-defined functions by hitting a single key while the mouse
focus is in the active plot window.  It is even possible to combine mouse
input with `batch` command scripts, by invoking the command `pause mouse`
and then using the mouse variables returned by mouse clicking as parameters
for subsequent scripted actions. See @ref{bind} and @ref{variables}.
See also the command `set mouse`.

@menu
* bind::                        
* Mouse_variables::             
@end menu

@node bind, Mouse_variables, mouse_input, mouse_input
@subsection bind

@c ?commands bind
@cindex bind

The @ref{bind} allows defining or redefining a hotkey, i.e. a sequence of gnuplot
commands which will be executed when a certain key or key sequence is pressed
while the driver's window has the input focus. Note that @ref{bind} is only
available if gnuplot was compiled with `mouse` support and it is used by all
mouse-capable terminals. Bindings overwrite the builtin bindings (like in
every real editor), except <space> and 'q' which cannot be rebound (unless
one exception, see below). Mouse buttons cannot be rebound.

You get the list of all hotkeys by typing @ref{bind} or by hitting 'h' in the
graph window.

Note that multikey-bindings with modifiers have to be quoted.

Normally hotkeys are only recognized when the currently active plot window
has focus. `bind allwindows <key> ...` (short form: `bind all <key> ...`)
causes the binding for <key> to apply to all gnuplot plot windows, active
or not.  In this case gnuplot variable MOUSE_KEY_WINDOW is set to the ID
of the originating window, and may be used by the bound command.

By default, the <space> hotkey raises gnuplot's command window. On some
terminals (e.g. x11, wx), 'q' closes the graph window. These defaults can
be changed to ctrl-space and ctrl-q by starting gnuplot as 'gnuplot -ctrlq',
see `x11 command-line-options`, or by the X Resource 'gnuplot*ctrlq'.
Note: if <space> (or ctrl-space) does not raise the gnuplot window under X11,
see discussion in @ref{raise}.

Syntax:
@example
      bind @{allwindows@} [<key-sequence>] ["<gnuplot commands>"]
      bind!

@end example

Examples:

- set bindings:

@example
    bind a "replot"
    bind "ctrl-a" "plot x*x"
    bind "ctrl-alt-a" 'print "great"'
    bind Home "set view 60,30; replot"
    bind all Home 'print "This is window ",MOUSE_KEY_WINDOW'

@end example

- show bindings:
@example
    bind "ctrl-a"          # shows the binding for ctrl-a
    bind                   # shows all bindings

@end example

- remove bindings:
@example
    bind "ctrl-alt-a" ""   # removes binding for ctrl-alt-a
                             (note that builtins cannot be removed)
    bind!                  # installs default (builtin) bindings

@end example

- bind a key to toggle something:
@example
  v=0
  bind "ctrl-r" "v=v+1;if(v%2)set term x11 noraise; else set term x11 raise"

@end example

Modifiers (ctrl / alt) are case insensitive, keys not:
@example
    ctrl-alt-a == CtRl-alT-a
    ctrl-alt-a != ctrl-alt-A

@end example

List of modifiers (alt == meta):
@example
    ctrl, alt

@end example

List of supported special keys:

@example
   "BackSpace", "Tab", "Linefeed", "Clear", "Return", "Pause", "Scroll_Lock",
   "Sys_Req", "Escape", "Delete", "Home", "Left", "Up", "Right", "Down",
   "PageUp", "PageDown", "End", "Begin",

@end example

@example
   "KP_Space", "KP_Tab", "KP_Enter", "KP_F1", "KP_F2", "KP_F3", "KP_F4",
   "KP_Home", "KP_Left", "KP_Up", "KP_Right", "KP_Down", "KP_PageUp",
   "KP_PageDown", "KP_End", "KP_Begin", "KP_Insert", "KP_Delete", "KP_Equal",
   "KP_Multiply", "KP_Add", "KP_Separator", "KP_Subtract", "KP_Decimal",
   "KP_Divide",

@end example

@example
   "KP_1" - "KP_9", "F1" - "F12"

@end example

See also help for `mouse` and @ref{if}.


@node Mouse_variables,  , bind, mouse_input
@subsection Mouse variables

@c ?mouse variables
When mousing is active, clicking in the active window will set several user
variables that can be accessed from the gnuplot command line. The coordinates
of the mouse at the time of the click are stored in MOUSE_X MOUSE_Y MOUSE_X2
and MOUSE_Y2. The mouse button clicked, and any meta-keys active at that time,
are stored in MOUSE_BUTTON MOUSE_SHIFT MOUSE_ALT and MOUSE_CTRL.  These
variables are set to undefined at the start of every plot, and only become
defined in the event of a mouse click in the active plot window. To determine
from a script if the mouse has been clicked in the active plot window, it is
sufficient to test for any one of these variables being defined.

@example
      plot 'something'
      pause mouse
      if (defined(MOUSE_BUTTON)) call 'something_else'; \
      else print "No mouse click."

@end example

It is also possible to track keystrokes in the plot window using the mousing
code.

@example
      plot 'something'
      pause mouse keypress
      print "Keystroke ", MOUSE_KEY, " at ", MOUSE_X, " ", MOUSE_Y

@end example

When `pause mouse keypress` is terminated by a keypress, then MOUSE_KEY will
contain the ascii character value of the key that was pressed. MOUSE_CHAR will
contain the character itself as a string variable.  If the pause command is
terminated abnormally (e.g. by ctrl-C or by externally closing the plot window)
then MOUSE_KEY will equal -1.

Note that after a zoom by mouse, you can read the new ranges as GPVAL_X_MIN,
GPVAL_X_MAX, GPVAL_Y_MIN, and GPVAL_Y_MAX, see @ref{variables}.



@node Plotting, Start-up, mouse_input, gnuplot
@section Plotting

@cindex plotting

There are three `gnuplot` commands which actually create a plot: `plot`,
`splot` and @ref{replot}.  `plot` generates 2-d plots, `splot` generates 3-d
plots (actually 2-d projections, of course), and @ref{replot} appends its
arguments to the previous `plot` or `splot` and executes the modified
command.

Much of the general information about plotting can be found in the discussion
of `plot`; information specific to 3-d can be found in the `splot` section.

`plot` operates in either rectangular or polar coordinates -- see `set polar`
for details of the latter.  `splot` operates only in rectangular coordinates,
but the @ref{mapping} command allows for a few other coordinate systems to be
treated.  In addition, the @ref{using} option allows both `plot` and `splot` to
treat almost any coordinate system you'd care to define.

`plot` also lets you use each of the four borders -- x (bottom), x2 (top), y
(left) and y2 (right) -- as an independent axis.  The `axes` option lets you
choose which pair of axes a given function or data set is plotted against.  A
full complement of `set` commands exists to give you complete control over
the scales and labelling of each axis.  Some commands have the name of an
axis built into their names, such as @ref{xlabel}.  Other commands have one
or more axis names as options, such as `set logscale xy`.  Commands and
options controlling the z axis have no effect on 2-d graphs.

`splot` can plot surfaces and contours in addition to points and/or lines.
In addition to `splot`, see @ref{isosamples} for information about defining
the grid for a 3-d function;  @ref{datafile} for information about the
requisite file structure for 3-d data values; and @ref{contour} and
@ref{cntrparam} for information about contours.

In `splot`, control over the scales and labels of the axes are the same as
with `plot`, except that commands and options controlling the x2 and y2 axes
have no effect whereas of course those controlling the z axis do take effect.

@node Start-up, String_constants_and_string_variables, Plotting, gnuplot
@section Start-up

@c ^ <a name="start-up"></a>
@cindex startup

@cindex start

@cindex .gnuplot

When `gnuplot` is run, it looks for an initialization file to load.
This file is called `.gnuplot` on Unix and AmigaOS systems, and
`GNUPLOT.INI` on other systems.  If this file is not found in the
current directory, the program will look for it in the HOME directory
(under AmigaOS, Atari(single)TOS, MS-DOS, Windows and OS/2, the
environment variable `GNUPLOT` should contain the name of this
directory; on Windows NT, it will use `USERPROFILE` if GNUPLOT isn't
defined).  Note: if NOCWDRC is defined during the installation,
`gnuplot` will not read from the current directory.

If the initialization file is found, `gnuplot` executes the commands in it.
These may be any legal `gnuplot` commands, but typically they are limited to
setting the terminal and defining frequently-used functions or variables.

@node String_constants_and_string_variables, Substitution_and_Command_line_macros, Start-up, gnuplot
@section String constants and string variables

@cindex strings

@c ?string variables
In addition to string constants, most gnuplot commands also accept a string
variable, a string expression, or a function that returns a string.
For example, the following four methods of creating a plot all result in the
same plot title:

@example
      four = "4"
      graph4 = "Title for plot #4"
      graph(n) = sprintf("Title for plot #%d",n)

@end example

@example
      plot 'data.4' title "Title for plot #4"
      plot 'data.4' title graph4
      plot 'data.4' title "Title for plot #".four
      plot 'data.4' title graph(4)

@end example

Since integers are promoted to strings when operated on by the string
concatenation operator, the following method also works:

@example
      N = 4
      plot 'data.'.N title "Title for plot #".N

@end example

In general, elements on the command line will only be evaluated as possible
string variables if they are not otherwise recognizable as part of the normal
gnuplot syntax. So the following sequence of commands is legal, although
probably should be avoided so as not to cause confusion:

@example
      plot = "my_datafile.dat"
      title = "My Title"
      plot plot title title

@end example

There are three binary operators that require string operands: the string
concatenation operator ".", the string equality operator "eq" and the string
inequality operator "ne".  The following example will print TRUE.

@example
     if ("A"."B" eq "AB") print "TRUE"

@end example

See also the two string formatting functions @ref{gprintf} and @ref{sprintf}.

@cindex substring

Substrings can be specified by appending a range specifier to any string,
string variable, or string-valued function.  The range specifier has the
form [begin:end], where begin is the index of the first character of the
substring and end is the index of the last character of the substring.
The first character has index 1.  The begin or end fields may be empty, or
contain '*', to indicate the true start or end of the original string.
E.g.  str[:] and str[*:*] both describe the full string str.

@node Substitution_and_Command_line_macros, Syntax, String_constants_and_string_variables, gnuplot
@section Substitution and Command line macros

@cindex substitution

When a command line to gnuplot is first read, i.e. before it is interpreted
or executed, two forms of lexical substitution are performed. These are
triggered by the presence of text in backquotes (ascii character 96) or
preceded by @@ (ascii character 64).

@menu
* Substitution_of_system_commands_in_backquotes::  
* Substitution_of_string_variables_as_macros::  
* String_variables::            
@end menu

@node Substitution_of_system_commands_in_backquotes, Substitution_of_string_variables_as_macros, Substitution_and_Command_line_macros, Substitution_and_Command_line_macros
@subsection Substitution of system commands in backquotes

@c ?substitution backquotes
@cindex backquotes

@c ?system commands
Command-line substitution is specified by a system command enclosed in
backquotes.  This command is spawned and the output it produces replaces
the backquoted text on the command line.  Some implementations also support
pipes;  see @ref{special-filenames}.

Command-line substitution can be used anywhere on the `gnuplot` command
line, except inside strings delimited by single quotes.

Example:

This will run the program `leastsq` and replace `leastsq` (including
backquotes) on the command line with its output:
@example
      f(x) = `leastsq`

@end example

or, in VMS
@example
      f(x) = `run leastsq`

@end example

These will generate labels with the current time and userid:
@example
      set label "generated on `date +%Y-%m-%d` by `whoami`" at 1,1
      set timestamp "generated on %Y-%m-%d by `whoami`"

@end example

@node Substitution_of_string_variables_as_macros, String_variables, Substitution_of_system_commands_in_backquotes, Substitution_and_Command_line_macros
@subsection Substitution of string variables as macros

@c ?substitution macros
@cindex macros
@opindex macros


@cindex exists
@findex exists


Substitution of command line macros is disabled by default, but may be
enabled using the @ref{macros} command.  If macro substitution is enabled,
the character @@ is used to trigger substitution of the current value of a
string variable into the command line. The text in the string variable may
contain any number of lexical elements.  This allows string variables to be
used as command line macros.  Only string constants may be expanded using this
mechanism, not string-valued expressions.
For example:

@example
      set macros
      style1 = "lines lt 4 lw 2"
      style2 = "points lt 3 pt 5 ps 2"
      range1 = "using 1:3"
      range2 = "using 1:5"
      plot "foo" @@range1 with @@style1, "bar" @@range2 with @@style2

@end example

The line containing @@ symbols is expanded on input, so that by the time it is
executed the effect is identical to having typed in full

@example
      plot "foo" using 1:3 with lines lt 4 lw 2, \
           "bar" using 1:5 with points lt 3 pt 5 ps 2

@end example

The function exists() may be useful in connection with macro evaluation.
The following example checks that C can safely be expanded as the name of
a user-defined variable:

@example
      C = "pi"
      if (exists(C)) print C," = ", @@C

@end example

Macro expansion does not occur inside either single or double quotes.
However macro expansion does occur inside backquotes.

@node String_variables,  , Substitution_of_string_variables_as_macros, Substitution_and_Command_line_macros
@subsection String variables, macros, and command line substitution

@cindex mixing_macros_backquotes

@c ?substitution mixing_macros_backquotes
The interaction of string variables, backquotes and macro substitution is
somewhat complicated.  Backquotes do not block macro substitution, so

@example
      filename = "mydata.inp"
      lines = ` wc --lines @@filename | sed "s/ .*//" `

@end example

results in the number of lines in mydata.inp being stored in the integer
variable lines. And double quotes do not block backquote substitution, so

@example
      mycomputer = "`uname -n`"

@end example

results in the string returned by the system command `uname -n` being stored
in the string variable mycomputer.

However, macro substitution is not performed inside double quotes, so you
cannot define a system command as a macro and then use both macro and backquote
substitution at the same time.

@example
       machine_id = "uname -n"
       mycomputer = "`@@machine_id`"  # doesn't work!!

@end example

This fails because the double quotes prevent @@machine_id from being interpreted
as a macro. To store a system command as a macro and execute it later you must
instead include the backquotes as part of the macro itself.  This is
accomplished by defining the macro as shown below.  Notice that the sprintf
format nests all three types of quotes.

@example
      machine_id = sprintf('"`uname -n`"')
      mycomputer = @@machine_id

@end example

@node Syntax, Time/Date_data, Substitution_and_Command_line_macros, gnuplot
@section Syntax

@cindex syntax

@cindex specify

@cindex punctuation

Version 4 of gnuplot is much less sensitive than earlier versions to the
order of keywords and suboptions. However, if you get error messages from
specifying options that you think should work, please try rearranging them
into the exact order listed by the documentation.

Options and any accompanying parameters are separated by spaces whereas lists
and coordinates are separated by commas.  Ranges are separated by colons and
enclosed in brackets [], text and file names are enclosed in quotes, and a
few miscellaneous things are enclosed in parentheses.  Braces @{@} are used for
a few special purposes.

Commas are used to separate coordinates on the `set` commands @ref{arrow},
@ref{key}, and @ref{label}; the list of variables being fitted (the list after the
`via` keyword on the @ref{fit} command); lists of discrete contours or the loop
parameters which specify them on the @ref{cntrparam} command; the arguments
of the `set` commands @ref{dgrid3d}, @ref{dummy}, @ref{isosamples}, @ref{offsets}, @ref{origin},
@ref{samples}, @ref{size}, `time`, and @ref{view}; lists of tics or the loop parameters
which specify them; the offsets for titles and axis labels; parametric
functions to be used to calculate the x, y, and z coordinates on the `plot`,
@ref{replot} and `splot` commands; and the complete sets of keywords specifying
individual plots (data sets or functions) on the `plot`, @ref{replot} and `splot`
commands.

Parentheses are used to delimit sets of explicit tics (as opposed to loop
parameters) and to indicate computations in the @ref{using} filter of the @ref{fit},
`plot`, @ref{replot} and `splot` commands.

(Parentheses and commas are also used as usual in function notation.)

Square brackets are used to delimit ranges given in `set`, `plot`
or `splot` commands.

Colons are used to separate extrema in `range` specifications (whether they
are given on `set`, `plot` or `splot` commands) and to separate entries in
the @ref{using} filter of the `plot`, @ref{replot}, `splot` and @ref{fit} commands.

Semicolons are used to separate commands given on a single command line.

Braces are used in text to be specially processed by some terminals, like
@ref{postscript}.  They are also used to denote complex numbers: @{3,2@} = 3 + 2i.

At present you should not embed \n inside @{@} when using the PostScript
terminal in `enhanced text` mode.

The EEPIC, Imagen, Uniplex, LaTeX, and TPIC drivers allow a newline to be
specified by \\ in a single-quoted string or \\\\ in a double-quoted string.

@menu
* Quote_Marks::                 
@end menu

@node Quote_Marks,  , Syntax, Syntax
@subsection Quote Marks

@cindex quotes

@c ?syntax quotes
Gnuplot uses three forms of quote marks for delimiting text strings,
double-quote (ascii 34), single-quote (ascii 39), and backquote (ascii 96).

Filenames may be entered with either single- or double-quotes.  In this
manual the command examples generally single-quote filenames and double-quote
other string tokens for clarity.

String constants and text strings used for labels, titles, or other plot
elements may be enclosed in either single quotes or double quotes. Further
processing of the quoted text depends on the choice of quote marks.

Backslash processing of special characters like \n (newline) and
\345 (octal character code) is performed for double-quoted strings.  In
single-quoted strings, backslashes are just ordinary characters.  To get
a single-quote (ascii 39) in a single-quoted string, it has to be doubled.
Thus the strings "d\" s' b\\" and 'd" s'' b\' are completely equivalent.

Text justification is the same for each line of a multi-line string.
Thus the center-justified string
@example
      "This is the first line of text.\nThis is the second line."
@end example

will produce
@example
                       This is the first line of text.
                          This is the second line.
@end example

but
@example
      'This is the first line of text.\nThis is the second line.'
@end example

will produce
@example
          This is the first line of text.\nThis is the second line.

@end example

Enhanced text processing is performed for both double-quoted text and
single-quoted text, but only by terminals supporting this mode.
See `enhanced text`.

Back-quotes are used to enclose system commands for substitution into the
command line.  See `substitution`.

@node Time/Date_data,  , Syntax, gnuplot
@section Time/Date data

@c ^ <a name="Time/Date data"></a>
@c ^ <a name="Time/date"></a>
@cindex time/date

`gnuplot` supports the use of time and/or date information as input data.
This feature is activated by the commands `set xdata time`, `set ydata time`,
etc.

Internally all times and dates are converted to the number of seconds from
the year 2000.  The command @ref{timefmt} defines the format for all inputs:
data files, ranges, tics, label positions---in short, anything that accepts a
data value must receive it in this format.  Since only one input format can
be in force at a given time, all time/date quantities being input at the same
time must be presented in the same format.  Thus if both x and y data in a
file are time/date, they must be in the same format.

The conversion to and from seconds assumes Universal Time (which is the same
as Greenwich Standard Time).  There is no provision for changing the time
zone or for daylight savings.  If all your data refer to the same time zone
(and are all either daylight or standard) you don't need to worry about these
things.  But if the absolute time is crucial for your application, you'll
need to convert to UT yourself.

Commands like @ref{xrange} will re-interpret the integer according to
@ref{timefmt}.  If you change @ref{timefmt}, and then `show` the quantity again, it
will be displayed in the new @ref{timefmt}.  For that matter, if you give the
deactivation command (like @ref{xdata}), the quantity will be shown in its
numerical form.

The commands `set format` or `set tics format`  define the format that will be
used for tic labels, whether or not the specified axis is time/date.

If time/date information is to be plotted from a file, the @ref{using} option
_must_ be used on the `plot` or `splot` command.  These commands simply use
white space to separate columns, but white space may be embedded within the
time/date string.  If you use tabs as a separator, some trial-and-error may
be necessary to discover how your system treats them.

The following example demonstrates time/date plotting.

Suppose the file "data" contains records like

@example
      03/21/95 10:00  6.02e23

@end example

This file can be plotted by

@example
      set xdata time
      set timefmt "%m/%d/%y"
      set xrange ["03/21/95":"03/22/95"]
      set format x "%m/%d"
      set timefmt "%m/%d/%y %H:%M"
      plot "data" using 1:3

@end example

which will produce xtic labels that look like "03/21".

See the descriptions of each command for more details.

@node Commands, Terminal_types, gnuplot, Top
@chapter Commands

@cindex commands

This section lists the commands acceptable to `gnuplot` in alphabetical
order.  Printed versions of this document contain all commands; on-line
versions may not be complete.  Indeed, on some systems there may be no
commands at all listed under this heading.

Note that in most cases unambiguous abbreviations for command names and their
options are permissible, i.e., "`p f(x) w li`" instead of "`plot f(x) with
lines`".

In the syntax descriptions, braces (@{@}) denote optional arguments and a
vertical bar (|) separates mutually exclusive choices.

@menu
* cd::                          
* call::                        
* clear::                       
* exit::                        
* fit::                         
* help::                        
* history::                     
* if::                          
* load::                        
* lower::                       
* pause::                       
* plot::                        
* print::                       
* pwd::                         
* quit::                        
* raise::                       
* replot::                      
* reread::                      
* reset::                       
* save::                        
* set-show::                    
* shell::                       
* splot::                       
* system_::                     
* test::                        
* undefine::                    
* unset::                       
* update::                      
@end menu

@node cd, call, Commands, Commands
@section cd

@c ?commands cd
@cindex cd
@cmindex cd


The @ref{cd} command changes the working directory.

Syntax:
@example
      cd '<directory-name>'

@end example

The directory name must be enclosed in quotes.

Examples:
@example
      cd 'subdir'
      cd ".."

@end example

It is recommended for DOS and Windows users to use
single-quotes---backslash [\] has special significance inside
double-quotes and has to be escaped.  For example,
@example
      cd "c:\newdata"
@end example

fails, but
@example
      cd 'c:\newdata'
      cd "c:\\newdata"
@end example

works as expected.

@node call, clear, cd, Commands
@section call

@c ?commands call
@cindex call
@cmindex call


The @ref{call} command is identical to the load command with one exception: you
can have up to ten additional parameters to the command (delimited according
to the standard parser rules) which can be substituted into the lines read
from the file.  As each line is read from the @ref{call}ed input file, it is
scanned for the sequence `$` (dollar-sign) followed by a digit (0--9).  If
found, the sequence is replaced by the corresponding parameter from the
@ref{call} command line.  If the parameter was specified as a string in the
@ref{call} line, it is substituted without its enclosing quotes.  Sequence `$#`
is replaced by the number of passed parameters.  `$` followed by any character
will be that character; e.g. use `$$` to get a single `$`.  Providing more
than ten parameters on the @ref{call} command line will cause an error.  A
parameter that was not provided substitutes as nothing.  Files being @ref{call}ed
may themselves contain @ref{call} or `load` commands.

The @ref{call} command _must_ be the last command on a multi-command line.

Syntax:
@example
      call "<input-file>" <parameter-0> <parm-1> ... <parm-9>

@end example

The name of the input file must be enclosed in quotes, and it is recommended
that parameters are similarly enclosed in quotes (future versions of gnuplot
may treat quoted and unquoted arguments differently).

Example:

If the file 'calltest.gp' contains the line:
@example
      print "argc=$# p0=$0 p1=$1 p2=$2 p3=$3 p4=$4 p5=$5 p6=$6 p7=x$7x"

@end example

entering the command:
@example
      call 'calltest.gp' "abcd" 1.2 + "'quoted'" -- "$2"

@end example

will display:
@example
      argc=7 p0=abcd p1=1.2 p2=+ p3='quoted' p4=- p5=- p6=$2 p7=xx

@end example

NOTE: there is a clash in syntax with the datafile @ref{using} callback
operator.  Use `$$n` or `column(n)` to access column n from a datafile inside
a @ref{call}ed datafile plot.

@node clear, exit, call, Commands
@section clear

@c ?commands clear
@cindex clear
@cmindex clear


The @ref{clear} command erases the current screen or output device as specified
by @ref{output}.  This usually generates a formfeed on hardcopy devices.  Use
@ref{terminal} to set the device type.

For some terminals @ref{clear} erases only the portion of the plotting surface
defined by @ref{size}, so for these it can be used in conjunction with @ref{multiplot} to create an inset.

Example:
@example
      set multiplot
      plot sin(x)
      set origin 0.5,0.5
      set size 0.4,0.4
      clear
      plot cos(x)
      unset multiplot

@end example

Please see @ref{multiplot}, @ref{size}, and @ref{origin} for details of these
commands.

@node exit, fit, clear, Commands
@section exit

@c ?commands exit
@cindex exit
@cmindex exit


The commands @ref{exit} and @ref{quit}, as well as the END-OF-FILE character (usually
Ctrl-D) terminate input from the current input stream: terminal session, pipe,
and file input (pipe).

If input streams are nested (inherited `load` scripts), then reading will
continue in the parent stream. When the top level stream is closed, the
program itself will exit.

The command `exit gnuplot` will immediately and unconditionally cause gnuplot
to exit even if the input stream is multiply nested.  In this case any open
output files may not be completed cleanly. Example of use:

@example
      bind "ctrl-x" "unset output; exit gnuplot"

@end example

See help for `batch/interactive` for more details.

@node fit, help, exit, Commands
@section fit

@c ?commands fit
@cindex fit
@cmindex fit


@cindex least-squares

@cindex Marquardt

The @ref{fit} command can fit a user-defined function to a set of data points
(x,y) or (x,y,z), using an implementation of the nonlinear least-squares
(NLLS) Marquardt-Levenberg algorithm.  Any user-defined variable occurring in
the function body may serve as a fit parameter, but the return type of the
function must be real.

Syntax:
@example
      fit @{[xrange] @{[yrange]@}@} <function> '<datafile>'
          @{datafile-modifiers@}
          via '<parameter file>' | <var1>@{,<var2>,...@}

@end example

Ranges may be specified to temporarily limit the data which is to be fitted;
any out-of-range data points are ignored. The syntax is
@example
      [@{dummy_variable=@}@{<min>@}@{:<max>@}],
@end example

analogous to `plot`; see @ref{ranges}.

<function> is any valid `gnuplot` expression, although it is usual to use a
previously user-defined function of the form f(x) or f(x,y).

<datafile> is treated as in the `plot` command.  All the @ref{datafile}
modifiers (@ref{using}, @ref{every},...) except @ref{smooth} and the deprecated @ref{thru}
are applicable to @ref{fit}. See @ref{datafile}.

The default data formats for fitting functions with a single independent
variable, y=f(x), are @{x:@}y or x:y:s; those formats can be changed with
the datafile @ref{using} qualifier.  The third item (a column number or an
expression), if present, is interpreted as the standard deviation of the
corresponding y value and is used to compute a weight for the datum, 1/s**2.
Otherwise, all data points are weighted equally, with a weight of one.
Note that if you don't specify a @ref{using} option at all, no y deviations are
read from the datafile even if it does have a third column, so you'll
always get unit weights.

To fit a function with two independent variables, z=f(x,y), the required
format is @ref{using} with four items, x:y:z:s.  The complete format must be
given---no default columns are assumed for a missing token.  Weights for
each data point are evaluated from 's' as above.  If error estimates are
not available, a constant value can be specified as a constant expression
(see @ref{using}), e.g., `using 1:2:3:(1)`.

Multiple datasets may be simultaneously fit with functions of one
independent variable by making y a 'pseudo-variable', e.g., the dataline
number, and fitting as two independent variables.  See @ref{multi-branch}.

The `via` qualifier specifies which parameters are to be adjusted, either
directly, or by referencing a parameter file.

Examples:
@example
      f(x) = a*x**2 + b*x + c
      g(x,y) = a*x**2 + b*y**2 + c*x*y
      FIT_LIMIT = 1e-6
      fit f(x) 'measured.dat' via 'start.par'
      fit f(x) 'measured.dat' using 3:($7-5) via 'start.par'
      fit f(x) './data/trash.dat' using 1:2:3 via a, b, c
      fit g(x,y) 'surface.dat' using 1:2:3:(1) via a, b, c

@end example

After each iteration step, detailed information about the current state
of the fit is written to the display.  The same information about the
initial and final states is written to a log file, "fit.log".  This file
is always appended to, so as to not lose any previous fit history;  it
should be deleted or renamed as desired. By using the command
`set fit logfile`, the name of the log file can be changed.

If gnuplot was built with this option, and you activated it using `set fit
errorvariables`, the error for each fitted parameter will be stored in
a variable named like the parameter, but with "_err" appended.  Thus the
errors can be used as input for further computations.

The fit may be interrupted by pressing Ctrl-C (any key but Ctrl-C under
MSDOS and Atari Multitasking Systems).  After the current iteration
completes, you have the option to (1) stop the fit and accept the current
parameter values, (2) continue the fit, (3) execute a `gnuplot` command
as specified by the environment variable FIT_SCRIPT.  The default for
FIT_SCRIPT is @ref{replot}, so if you had previously plotted both the data
and the fitting function in one graph, you can display the current state
of the fit.

Once @ref{fit} has finished, the @ref{update} command may be used to store final
values in a file for subsequent use as a parameter file.   See @ref{update}
for details.

@menu
* adjustable_parameters::       
* short_introduction::          
* error_estimates::             
* control::                     
* multi-branch::                
* starting_values::             
* tips::                        
@end menu

@node adjustable_parameters, short_introduction, fit, fit
@subsection adjustable parameters

@c ?commands fit parameters
@c ?fit parameters
@c ?commands fit adjustable_parameters
@c ?fit adjustable_parameters
@cindex fit_parameters

There are two ways that `via` can specify the parameters to be adjusted,
either directly on the command line or indirectly, by referencing a
parameter file.  The two use different means to set initial values.

Adjustable parameters can be specified by a comma-separated list of variable
names after the `via` keyword.  Any variable that is not already defined
is created with an initial value of 1.0.  However, the fit is more likely
to converge rapidly if the variables have been previously declared with more
appropriate starting values.

In a parameter file, each parameter to be varied and a corresponding initial
value are specified, one per line, in the form
@example
      varname = value

@end example

Comments, marked by '#', and blank lines are permissible.  The
special form
@example
      varname = value       # FIXED

@end example

means that the variable is treated as a 'fixed parameter', initialized by the
parameter file, but not adjusted by @ref{fit}.  For clarity, it may be useful to
designate variables as fixed parameters so that their values are reported by
@ref{fit}.  The keyword `# FIXED` has to appear in exactly this form.


@node short_introduction, error_estimates, adjustable_parameters, fit
@subsection short introduction

@c ?commands fit beginners_guide
@c ?fit beginners_guide
@c ?fit guide
@cindex fitting

@ref{fit} is used to find a set of parameters that 'best' fits your data to your
user-defined function.  The fit is judged on the basis of the sum of the
squared differences or 'residuals' (SSR) between the input data points and
the function values, evaluated at the same places.  This quantity is often
called 'chisquare' (i.e., the Greek letter chi, to the power of 2).  The
algorithm attempts to minimize SSR, or more precisely, WSSR, as the residuals
are 'weighted' by the input data errors (or 1.0) before being squared;
see `fit error_estimates` for details.

That's why it is called 'least-squares fitting'.  Let's look at an example
to see what is meant by 'non-linear', but first we had better go over some
terms.  Here it is convenient to use z as the dependent variable for
user-defined functions of either one independent variable, z=f(x), or two
independent variables, z=f(x,y).  A parameter is a user-defined variable
that @ref{fit} will adjust, i.e., an unknown quantity in the function
declaration.  Linearity/non-linearity refers to the relationship of the
dependent variable, z, to the parameters which @ref{fit} is adjusting, not of
z to the independent variables, x and/or y.  (To be technical, the
second @{and higher@} derivatives of the fitting function with respect to
the parameters are zero for a linear least-squares problem).

For linear least-squares (LLS), the user-defined function will be a sum of
simple functions, not involving any parameters, each multiplied by one
parameter.  NLLS handles more complicated functions in which parameters can
be used in a large number of ways.  An example that illustrates the
difference between linear and nonlinear least-squares is the Fourier series.
One member may be written as
@example
     z=a*sin(c*x) + b*cos(c*x).
@end example

If a and b are the unknown parameters and c is constant, then estimating
values of the parameters is a linear least-squares problem.  However, if
c is an unknown parameter, the problem is nonlinear.

In the linear case, parameter values can be determined by comparatively
simple linear algebra, in one direct step.  However LLS is a special case
which is also solved along with more general NLLS problems by the iterative
procedure that `gnuplot` uses.  @ref{fit} attempts to find the minimum by doing
a search.  Each step (iteration) calculates WSSR with a new set of parameter
values.  The Marquardt-Levenberg algorithm selects the parameter values for
the next iteration.  The process continues until a preset criterion is met,
either (1) the fit has "converged" (the relative change in WSSR is less than
FIT_LIMIT), or (2) it reaches a preset iteration count limit, FIT_MAXITER
(see @ref{variables}).  The fit may also be interrupted
and subsequently halted from the keyboard (see @ref{fit}).  The user variable
FIT_CONVERGED contains 1 if the previous fit command terminated due to
convergence; it contains 0 if the previous fit terminated for any other
reason.

Often the function to be fitted will be based on a model (or theory) that
attempts to describe or predict the behaviour of the data.  Then @ref{fit} can
be used to find values for the free parameters of the model, to determine
how well the data fits the model, and to estimate an error range for each
parameter.  See `fit error_estimates`.

Alternatively, in curve-fitting, functions are selected independent of
a model (on the basis of experience as to which are likely to describe
the trend of the data with the desired resolution and a minimum number
of parameters*functions.)  The @ref{fit} solution then provides an analytic
representation of the curve.

However, if all you really want is a smooth curve through your data points,
the @ref{smooth} option to `plot` may be what you've been looking for rather
than @ref{fit}.

@node error_estimates, control, short_introduction, fit
@subsection error estimates

@c ?commands fit error_estimates
@c ?fit error_estimates
@c ?fit errors
In @ref{fit}, the term "error" is used in two different contexts, data error
estimates and parameter error estimates.

Data error estimates are used to calculate the relative weight of each data
point when determining the weighted sum of squared residuals, WSSR or
chisquare.  They can affect the parameter estimates, since they determine
how much influence the deviation of each data point from the fitted function
has on the final values.  Some of the @ref{fit} output information, including
the parameter error estimates, is more meaningful if accurate data error
estimates have been provided.

The 'statistical overview' describes some of the @ref{fit} output and gives some
background for the 'practical guidelines'.

@menu
* statistical_overview::        
* practical_guidelines::        
@end menu

@node statistical_overview, practical_guidelines, error_estimates, error_estimates
@subsubsection statistical overview

@c ?commands fit error statistical_overview
@c ?fit error statistical_overview
@cindex statistical_overview

The theory of non-linear least-squares (NLLS) is generally described in terms
of a normal distribution of errors, that is, the input data is assumed to be
a sample from a population having a given mean and a Gaussian (normal)
distribution about the mean with a given standard deviation.  For a sample of
sufficiently large size, and knowing the population standard deviation, one
can use the statistics of the chisquare distribution to describe a "goodness
of fit" by looking at the variable often called "chisquare".  Here, it is
sufficient to say that a reduced chisquare (chisquare/degrees of freedom,
where degrees of freedom is the number of datapoints less the number of
parameters being fitted) of 1.0 is an indication that the weighted sum of
squared deviations between the fitted function and the data points is the
same as that expected for a random sample from a population characterized by
the function with the current value of the parameters and the given standard
deviations.

If the standard deviation for the population is not constant, as in counting
statistics where variance = counts, then each point should be individually
weighted when comparing the observed sum of deviations and the expected sum
of deviations.

At the conclusion @ref{fit} reports 'stdfit', the standard deviation of the fit,
which is the rms of the residuals, and the variance of the residuals, also
called 'reduced chisquare' when the data points are weighted.  The number of
degrees of freedom (the number of data points minus the number of fitted
parameters) is used in these estimates because the parameters used in
calculating the residuals of the datapoints were obtained from the same data.
These values are exported to the variables
@example
      FIT_NDF = Number of degrees of freedom
      FIT_WSSR = Weighted sum-of-squares residual
      FIT_STDFIT = sqrt(WSSR/NDF)

@end example

To estimate confidence levels for the parameters, one can use the minimum
chisquare obtained from the fit and chisquare statistics to determine the
value of chisquare corresponding to the desired confidence level, but
considerably more calculation is required to determine the combinations of
parameters which produce such values.

Rather than determine confidence intervals, @ref{fit} reports parameter error
estimates which are readily obtained from the variance-covariance matrix
after the final iteration.  By convention, these estimates are called
"standard errors" or "asymptotic standard errors", since they are calculated
in the same way as the standard errors (standard deviation of each parameter)
of a linear least-squares problem, even though the statistical conditions for
designating the quantity calculated to be a standard deviation are not
generally valid for the NLLS problem.  The asymptotic standard errors are
generally over-optimistic and should not be used for determining confidence
levels, but are useful for qualitative purposes.

The final solution also produces a correlation matrix, which gives an
indication of the correlation of parameters in the region of the solution;
if one parameter is changed, increasing chisquare, does changing another
compensate?  The main diagonal elements, autocorrelation, are all 1; if
all parameters were independent, all other elements would be nearly 0.  Two
variables which completely compensate each other would have an off-diagonal
element of unit magnitude, with a sign depending on whether the relation is
proportional or inversely proportional.  The smaller the magnitudes of the
off-diagonal elements, the closer the estimates of the standard deviation
of each parameter would be to the asymptotic standard error.

@node practical_guidelines,  , statistical_overview, error_estimates
@subsubsection practical guidelines

@c ?commands fit error practical_guidelines
@c ?fit error practical_guidelines
@cindex practical_guidelines

@cindex guidelines

If you have a basis for assigning weights to each data point, doing so lets
you make use of additional knowledge about your measurements, e.g., take into
account that some points may be more reliable than others.  That may affect
the final values of the parameters.

Weighting the data provides a basis for interpreting the additional @ref{fit}
output after the last iteration.  Even if you weight each point equally,
estimating an average standard deviation rather than using a weight of 1
makes WSSR a dimensionless variable, as chisquare is by definition.

Each fit iteration will display information which can be used to evaluate
the progress of the fit.  (An '*' indicates that it did not find a smaller
WSSR and is trying again.)  The 'sum of squares of residuals', also called
'chisquare', is the WSSR between the data and your fitted function; @ref{fit}
has minimized that.  At this stage, with weighted data, chisquare is expected
to approach the number of degrees of freedom (data points minus parameters).
The WSSR can be used to calculate the reduced chisquare (WSSR/ndf) or stdfit,
the standard deviation of the fit, sqrt(WSSR/ndf).  Both of these are
reported for the final WSSR.

If the data are unweighted, stdfit is the rms value of the deviation of the
data from the fitted function, in user units.

If you supplied valid data errors, the number of data points is large enough,
and the model is correct, the reduced chisquare should be about unity.  (For
details, look up the 'chi-squared distribution' in your favourite statistics
reference.)  If so, there are additional tests, beyond the scope of this
overview, for determining how well the model fits the data.

A reduced chisquare much larger than 1.0 may be due to incorrect data error
estimates, data errors not normally distributed, systematic measurement
errors, 'outliers', or an incorrect model function.  A plot of the residuals,
e.g., `plot 'datafile' using 1:($2-f($1))`, may help to show any systematic
trends.  Plotting both the data points and the function may help to suggest
another model.

Similarly, a reduced chisquare less than 1.0 indicates WSSR is less than that
expected for a random sample from the function with normally distributed
errors.  The data error estimates may be too large, the statistical
assumptions may not be justified, or the model function may be too general,
fitting fluctuations in a particular sample in addition to the underlying
trends.  In the latter case, a simpler function may be more appropriate.

You'll have to get used to both @ref{fit} and the kind of problems you apply it
to before you can relate the standard errors to some more practical estimates
of parameter uncertainties or evaluate the significance of the correlation
matrix.

Note that @ref{fit}, in common with most NLLS implementations, minimizes the
weighted sum of squared distances (y-f(x))**2.  It does not provide any means
to account for "errors" in the values of x, only in y.  Also, any "outliers"
(data points outside the normal distribution of the model) will have an
exaggerated effect on the solution.

@node control, multi-branch, error_estimates, fit
@subsection control

@c ?commands fit control
@c ?fit control
There are a number of `gnuplot` variables that can be defined to affect
@ref{fit}.  Those which can be defined once `gnuplot` is running are listed
under 'control_variables' while those defined before starting `gnuplot`
are listed under 'environment_variables'.

@menu
* control_variables::           
* environment_variables::       
@end menu

@node control_variables, environment_variables, control, control
@subsubsection control variables

@c ?commands fit control variables
@c ?fit control variables
The default epsilon limit (1e-5) may be changed by declaring a value for
@example
      FIT_LIMIT
@end example

When the sum of squared residuals changes between two iteration steps by
a factor less than this number (epsilon), the fit is considered to have
'converged'.

The maximum number of iterations may be limited by declaring a value for
@example
      FIT_MAXITER
@end example

A value of 0 (or not defining it at all)  means that there is no limit.

If you need even more control about the algorithm, and know the
Marquardt-Levenberg algorithm well, there are some more variables to
influence it. The startup value of `lambda` is normally calculated
automatically from the ML-matrix, but if you want to, you may provide
your own one with
@example
      FIT_START_LAMBDA
@end example

Specifying FIT_START_LAMBDA as zero or less will re-enable the automatic
selection. The variable
@example
      FIT_LAMBDA_FACTOR
@end example

gives the factor by which `lambda` is increased or decreased whenever
the chi-squared target function increased or decreased significantly.
Setting FIT_LAMBDA_FACTOR to zero re-enables the default factor of
10.0.

Other variables with the FIT_ prefix may be added to @ref{fit}, so it is safer
not to use that prefix for user-defined variables.

The variables FIT_SKIP and FIT_INDEX were used by earlier releases of
`gnuplot` with a 'fit' patch called `gnufit` and are no longer available.
The datafile @ref{every} modifier provides the functionality of FIT_SKIP.
FIT_INDEX was used for multi-branch fitting, but multi-branch fitting of
one independent variable is now done as a pseudo-3D fit in which the
second independent variable and @ref{using} are used to specify the branch.
See @ref{multi-branch}.

@node environment_variables,  , control_variables, control
@subsubsection environment variables

@c ?commands fit control environment
@c ?fit control environment
The environment variables must be defined before `gnuplot` is executed; how
to do so depends on your operating system.

@example
      FIT_LOG
@end example

changes the name (and/or path) of the file to which the fit log will be
written from the default of "fit.log" in the working directory. The default
value can be overwritten using the command `set fit logfile`.

@example
      FIT_SCRIPT
@end example

specifies a command that may be executed after an user interrupt. The default
is @ref{replot}, but a `plot` or `load` command may be useful to display a plot
customized to highlight the progress of the fit.

@node multi-branch, starting_values, control, fit
@subsection multi-branch

@c ?commands fit multi-branch
@c ?fit multi-branch
@cindex multi-branch

@cindex branch

In multi-branch fitting, multiple data sets can be simultaneously fit with
functions of one independent variable having common parameters by minimizing
the total WSSR.  The function and parameters (branch) for each data set are
selected by using a 'pseudo-variable', e.g., either the dataline number (a
'column' index of -1) or the datafile index (-2), as the second independent
variable.

Example:  Given two exponential decays of the form, z=f(x), each describing
a different data set but having a common decay time, estimate the values of
the parameters.  If the datafile has the format x:z:s, then
@example
     f(x,y) = (y==0) ? a*exp(-x/tau) : b*exp(-x/tau)
     fit f(x,y) 'datafile' using  1:-2:2:3  via a, b, tau

@end example

For a more complicated example, see the file "hexa.fnc" used by the
"fit.dem" demo.

Appropriate weighting may be required since unit weights may cause one
branch to predominate if there is a difference in the scale of the dependent
variable.  Fitting each branch separately, using the multi-branch solution
as initial values, may give an indication as to the relative effect of each
branch on the joint solution.

@node starting_values, tips, multi-branch, fit
@subsection starting values

@c ?commands fit starting_values
@c ?fit starting_values
@cindex starting_values

Nonlinear fitting is not guaranteed to converge to the global optimum (the
solution with the smallest sum of squared residuals, SSR), and can get stuck
at a local minimum.  The routine has no way to determine that;  it is up to
you to judge whether this has happened.

@ref{fit} may, and often will get "lost" if started far from a solution, where
SSR is large and changing slowly as the parameters are varied, or it may
reach a numerically unstable region (e.g., too large a number causing a
floating point overflow) which results in an "undefined value" message
or `gnuplot` halting.

To improve the chances of finding the global optimum, you should set the
starting values at least roughly in the vicinity of the solution, e.g.,
within an order of magnitude, if possible.  The closer your starting values
are to the solution, the less chance of stopping at another minimum.  One way
to find starting values is to plot data and the fitting function on the same
graph and change parameter values and @ref{replot} until reasonable similarity
is reached.  The same plot is also useful to check whether the fit stopped at
a minimum with a poor fit.

Of course, a reasonably good fit is not proof there is not a "better" fit (in
either a statistical sense, characterized by an improved goodness-of-fit
criterion, or a physical sense, with a solution more consistent with the
model.)  Depending on the problem, it may be desirable to @ref{fit} with various
sets of starting values, covering a reasonable range for each parameter.

@node tips,  , starting_values, fit
@subsection tips

@c ?commands fit tips
@c ?fit tips
@cindex tips

Here are some tips to keep in mind to get the most out of @ref{fit}.  They're not
very organized, so you'll have to read them several times until their essence
has sunk in.

The two forms of the `via` argument to @ref{fit} serve two largely distinct
purposes.  The `via "file"` form is best used for (possibly unattended) batch
operation, where you just supply the startup values in a file and can later
use @ref{update} to copy the results back into another (or the same) parameter
file.

The `via var1, var2, ...` form is best used interactively, where the command
history mechanism may be used to edit the list of parameters to be fitted or
to supply new startup values for the next try.  This is particularly useful
for hard problems, where a direct fit to all parameters at once won't work
without good starting values.  To find such, you can iterate several times,
fitting only some of the parameters, until the values are close enough to the
goal that the final fit to all parameters at once will work.

Make sure that there is no mutual dependency among parameters of the function
you are fitting.  For example, don't try to fit a*exp(x+b), because
a*exp(x+b)=a*exp(b)*exp(x).  Instead, fit either a*exp(x) or exp(x+b).

A technical issue:  the parameters must not be too different in magnitude.
The larger the ratio of the largest and the smallest absolute parameter
values, the slower the fit will converge.  If the ratio is close to or above
the inverse of the machine floating point precision, it may take next to
forever to converge, or refuse to converge at all.  You will have to adapt
your function to avoid this, e.g., replace 'parameter' by '1e9*parameter' in
the function definition, and divide the starting value by 1e9.

If you can write your function as a linear combination of simple functions
weighted by the parameters to be fitted, by all means do so.  That helps a
lot, because the problem is no longer nonlinear and should converge with only
a small number of iterations, perhaps just one.

Some prescriptions for analysing data, given in practical experimentation
courses, may have you first fit some functions to your data, perhaps in a
multi-step process of accounting for several aspects of the underlying
theory one by one, and then extract the information you really wanted from
the fitting parameters of those functions.  With @ref{fit}, this may often be
done in one step by writing the model function directly in terms of the
desired parameters.  Transforming data can also quite often be avoided,
though sometimes at the cost of a more difficult fit problem.  If you think
this contradicts the previous paragraph about simplifying the fit function,
you are correct.

A "singular matrix" message indicates that this implementation of the
Marquardt-Levenberg algorithm can't calculate parameter values for the next
iteration.  Try different starting values, writing the function in another
form, or a simpler function.

Finally, a nice quote from the manual of another fitting package (fudgit),
that kind of summarizes all these issues:  "Nonlinear fitting is an art!"

@node help, history, fit, Commands
@section help

@c ?commands help
@cindex help
@cmindex help


The @ref{help} command displays on-line help. To specify information on a
particular topic use the syntax:

@example
      help @{<topic>@}

@end example

If <topic> is not specified, a short message is printed about `gnuplot`.
After help for the requested topic is given, a menu of subtopics is given;
help for a subtopic may be requested by typing its name, extending the help
request.  After that subtopic has been printed, the request may be extended
again or you may go back one level to the previous topic.  Eventually, the
`gnuplot` command line will return.

If a question mark (?) is given as the topic, the list of topics currently
available is printed on the screen.

@node history, if, help, Commands
@section history

@c ?commands history
@cindex history
@cmindex history


`history` command lists or saves previous entries in the history of the
command line editing, or executes an entry.

Here you find 'usage by examples':

@example
      history               # show the complete history
      history 5             # show last 5 entries in the history
      history quiet 5       # show last 5 entries without entry numbers
      history "hist.gp"     # write the complete history to file hist.gp
      history "hist.gp" append # append the complete history to file hist.gp
      history 10 "hist.gp"  # write last 10 commands to file hist.gp
      history 10 "|head -5 >>diary.gp" # write 5 history commands using pipe
      history ?load         # show all history entries starting with "load"
      history ?"set c"      # like above, several words enclosed in quotes
      hi !reread            # execute last entry starting with "reread"
      hist !"set xr"        # like above, several words enclosed in quotes
      hi !hi                # guess yourself :-))

@end example

On systems which support a popen function (Unix), the output of history can be
piped through an external program by starting the file name with a '|', as one
of the above examples demonstrates.

@node if, load, history, Commands
@section if

@c ?commands if
@cindex if
@cmindex if


The @ref{if} command allows commands to be executed conditionally.

Syntax:
@example
      if (<condition>) <command-line> [; else if (<condition>) ...; else ...]

@end example

<condition> will be evaluated.  If it is true (non-zero), then the command(s)
of the <command-line> will be executed.  If <condition> is false (zero), then
the entire <command-line> is ignored until the next occurrence of `else`.
Note that use of `;` to allow multiple commands on the same line will
_not_ end the conditionalized commands.

Examples:
@example
      pi=3
      if (pi!=acos(-1)) print "?Fixing pi!"; pi=acos(-1); print pi
@end example

will display:
@example
      ?Fixing pi!
      3.14159265358979
@end example

but
@example
      if (1==2) print "Never see this"; print "Or this either"
@end example

will not display anything.

else:
@example
      v=0
      v=v+1; if (v%2) print "2" ; else if (v%3) print "3"; else print "fred"
@end example

(repeat the last line repeatedly!)

See @ref{reread} for an example of how @ref{if} and @ref{reread} can be used together to
perform a loop.

@node load, lower, if, Commands
@section load

@c ?commands load
@cindex load
@cmindex load


The `load` command executes each line of the specified input file as if it
had been typed in interactively.  Files created by the @ref{save} command can
later be `load`ed.  Any text file containing valid commands can be created
and then executed by the `load` command.  Files being `load`ed may themselves
contain `load` or @ref{call} commands.  See `comments` for information about
comments in commands.  To `load` with arguments, see @ref{call}.

The `load` command _must_ be the last command on a multi-command line.

Syntax:
@example
      load "<input-file>"

@end example

The name of the input file must be enclosed in quotes.

The special filename "-" may be used to `load` commands from standard input.
This allows a `gnuplot` command file to accept some commands from standard
input.  Please see help for `batch/interactive` for more details.

On some systems which support a popen function (Unix), the load file can be
read from a pipe by starting the file name with a '<'.

Examples:
@example
      load 'work.gnu'
      load "func.dat"
      load "< loadfile_generator.sh"

@end example

The `load` command is performed implicitly on any file names given as
arguments to `gnuplot`.  These are loaded in the order specified, and
then `gnuplot` exits.

@node lower, pause, load, Commands
@section lower

@c ?commands lower
@cindex lower
@cmindex lower


Syntax:
@example
      lower @{plot_window_nb@}

@end example

The @ref{lower} command lowers (opposite to @ref{raise}) plot window(s) associated
with the interactive terminal of your gnuplot session, i.e. `pm`, `win`, `wxt`
or `x11`. It puts the plot window to bottom in the z-order windows stack of
the window manager of your desktop.

As `x11` and `wxt` support multiple plot windows, then by default they lower
these windows in descending order of most recently created on top to the least
recently created on bottom. If a plot number is supplied as an optional
parameter, only the associated plot window will be lowered if it exists.

The optional parameter is ignored for single plot-window terminals, i.e. `pm`
and `win`.

@node pause, plot, lower, Commands
@section pause

@c ?commands pause
@cindex pause
@cmindex pause


@c ?pause mouse
The @ref{pause} command displays any text associated with the command and then
waits a specified amount of time or until the carriage return is pressed.
@ref{pause} is especially useful in conjunction with `load` files.

Syntax:
@example
      pause <time> @{"<string>"@}
      pause mouse @{<endcondition>@}@{, <endcondition>@} @{"<string>"@}

@end example

<time> may be any constant or expression.  Choosing -1 will wait until a
carriage return is hit, zero (0) won't pause at all, and a positive number
will wait the specified number of seconds.  The time is rounded to an integer
number of seconds if subsecond time resolution is not supported by the given
platform.  `pause 0` is synonymous with @ref{print}.

If the current terminal supports mousing, then `pause mouse` will terminate
on either a mouse click or on ctrl-C.  For all other terminals, or if mousing
is not active, `pause mouse` is equivalent to `pause -1`.

If one or more end conditions are given after `pause mouse`, then any one of
the conditions will terminate the pause. The possible end conditions are
`keypress`, `button1`, `button2`, `button3`, `close`, and `any`.
If the pause terminates on a keypress, then the ascii value of the key pressed
is returned in MOUSE_KEY.  The character itself is returned as a one character
string in MOUSE_CHAR. Hotkeys (bind command) are disabled if keypress is one of
the end conditions.  Zooming is disabled if button3 is one of the end 
conditions. 

In all cases the coordinates of the mouse are returned in variables MOUSE_X,
MOUSE_Y, MOUSE_X2, MOUSE_Y2.  See @ref{variables}.

Note: Since @ref{pause} communicates with the operating system rather than the
graphics, it may behave differently with different device drivers (depending
upon how text and graphics are mixed).

Examples:
@example
      pause -1    # Wait until a carriage return is hit
      pause 3     # Wait three seconds
      pause -1  "Hit return to continue"
      pause 10  "Isn't this pretty?  It's a cubic spline."
      pause mouse "Click any mouse button on selected data point"
      pause mouse keypress "Type a letter from A-F in the active window"
      pause mouse button1,keypress
      pause mouse any "Any key or button will terminate"

@end example

The variant "pause mouse key" will resume after any keypress in the active
plot window. If you want to wait for a particular key to be pressed, you can
use a reread loop such as:

@example
      printf "I will resume after you hit the Tab key in the plot window"
      load "wait_for_tab"

@end example

File "wait_for_tab" contains the lines

@example
      pause mouse key
      if (MOUSE_KEY != 9) reread

@end example


@node plot, print, pause, Commands
@section plot

@c ?commands plot
@cindex plot
@cmindex plot


`plot` is the primary command for drawing plots with `gnuplot`.  It creates
plots of functions and data in many, many ways.  `plot` is used to draw 2-d
functions and data; `splot` draws 2-d projections of 3-d surfaces and data.
`plot` and `splot` contain many common features; see `splot` for differences.
Note specifically that although the `binary <binary list>` variation does
work for both `plot` and `splot`, there are small differences between these
modes.  Furthermore, `plot`'s `axes` option does not exist for `splot`.

Syntax:
@example
      plot @{<ranges>@}
           @{<function> | @{"<datafile>" @{datafile-modifiers@}@}@}
           @{axes <axes>@} @{<title-spec>@} @{with <style>@}
           @{, @{definitions,@} <function> ...@}

@end example

where either a <function> or the name of a data file enclosed in quotes is
supplied.  A function is a mathematical expression or a pair of mathematical
expressions in parametric mode.  The expressions may be defined completely or
in part earlier in the stream of `gnuplot` commands (see `user-defined`).

It is also possible to define functions and parameters on the `plot` command
itself.  This is done merely by isolating them from other items with commas.

There are four possible sets of axes available; the keyword <axes> is used to
select the axes for which a particular line should be scaled.  `x1y1` refers
to the axes on the bottom and left; `x2y2` to those on the top and right;
`x1y2` to those on the bottom and right; and `x2y1` to those on the top and
left.  Ranges specified on the `plot` command apply only to the first set of
axes (bottom left).

Examples:
@example
      plot sin(x)
      plot f(x) = sin(x*a), a = .2, f(x), a = .4, f(x)
      plot [t=1:10] [-pi:pi*2] tan(t), \
           "data.1" using (tan($2)):($3/$4) smooth csplines \
                    axes x1y2 notitle with lines 5

@end example

See also `show plot`.

@menu
* data::                        
* errorbars::                   
* errorlines::                  
* parametric::                  
* ranges::                      
* title::                       
* with::                        
@end menu

@node data, errorbars, plot, plot
@subsection data

@c ?commands plot datafile
@c ?plot datafile
@cindex data-file

@cindex datafile
@opindex datafile


@cindex data

@cindex file

Discrete data contained in a file can be displayed by specifying the name of
the data file (enclosed in single or double quotes) on the `plot` command line.

Syntax:
@example
      plot '<file_name>' @{binary <binary list>@}
                         @{matrix@}
                         @{index <index list>@}
                         @{every <every list>@}
                         @{thru <thru expression>@}
                         @{using <using list>@}
                         @{smooth <option>@}

@end example

The modifiers `binary`, @ref{index}, @ref{every}, @ref{thru}, @ref{using}, and @ref{smooth} are
discussed separately.  In brief, `binary` allows data entry from a binary
file (default is ASCII), @ref{index} selects which data sets in a multi-data-set
file are to be plotted, @ref{every} specifies which points within a single data
set are to be plotted, @ref{using} determines how the columns within a single
record are to be interpreted (@ref{thru} is a special case of @ref{using}), and
@ref{smooth} allows for simple interpolation and approximation.  (`splot` has a
similar syntax, but does not support the @ref{smooth} and @ref{thru} options.)


ASCII DATA FILES:

Data files should contain at least one data point per record (@ref{using}
can select one data point from the record). Records beginning with `#`
(and also with `!` on VMS) will be treated as comments and ignored.
Each data point represents an (x,y) pair. For `plot`s with error bars or
error bars with lines (see @ref{errorbars} or @ref{errorlines}),
each data point is (x,y,ydelta), (x,y,ylow,yhigh),
(x,y,xdelta), (x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh).

In all cases, the numbers of each record of a data file must be separated
by white space (one or more blanks or tabs) unless a format specifier is
provided by the @ref{using} option. This white space divides each record into
columns. However, whitespace inside a pair of double quotes is ignored when
counting columns, so the following datafile line has three columns:
@example
      1.0 "second column" 3.0

@end example

Data may be written in exponential format with the exponent preceded by the
letter e or E.  The fortran exponential specificiers d, D, q, and Q may also
be used if the command `set datafile fortran` is in effect.

Only one column (the y value) need be provided.  If x is omitted, `gnuplot`
provides integer values starting at 0.

In datafiles, blank records (records with no characters other than blanks and
a newline and/or carriage return) are significant.

Single blank records designate discontinuities in a `plot`; no line will join
points separated by a blank records (if they are plotted with a line style).

Two blank records in a row indicate a break between separate data sets.
See @ref{index}.

If autoscaling has been enabled (@ref{autoscale}), the axes are automatically
extended to include all datapoints, with a whole number of tic marks if tics
are being drawn.  This has two consequences: i) For `splot`, the corner of
the surface may not coincide with the corner of the base.  In this case, no
vertical line is drawn.  ii) When plotting data with the same x range on a
dual-axis graph, the x coordinates may not coincide if the x2tics are not
being drawn.  This is because the x axis has been autoextended to a whole
number of tics, but the x2 axis has not.  The following example illustrates
the problem:

@example
      reset; plot '-', '-' axes x2y1
      1 1
      19 19
      e
      1 1
      19 19
      e

@end example

To avoid this, you can use the `fixmin`/`fixmax` feature of the
@ref{autoscale} command, which turns off the automatic extension of the
axis range upto the next tic mark.


BINARY DATA FILES:

Gnuplot can read binary data files.  However, adequate information about
details of the file format must be given on the command line or extracted
from the file itself for a supported binary `filetype`.  In particular,
there are two structures for binary files, a matrix binary format and a
general binary format.

The matrix binary format contains a two dimensional array of 32 bit IEEE
float values with an additional column and row of coordinate values.  As
with ASCII matrix, in the @ref{using} list, repetition of the coordinate row
constitutes column 1, repetition of the coordinate column constitutes
column 2, and the array of values constitutes column 3.

The general binary format contains an arbitrary number of columns for which
information must be specified at the command line.  For example, `array`,
`record`, `format` and @ref{using} can indicate the size, format and dimension
of data.  There are a variety of useful commands for skipping file headers
and changing endianess.  There are a set of commands for positioning and
translating data since often coordinates are not part of the file when
uniform sampling is inherent in the data.  Different from matrix binary or
ASCII, general binary does not treat the generated columns as 1, 2 or 3 in
the @ref{using} list.  Rather, column 1 begins with column 1 of the file, or as
specified in the `format` list.

There are global default settings for the various binary options which may
be set using the same syntax as the options when used as part of the `(s)plot
<filename> binary ...` command.  This syntax is `set datafile binary ...`.
The general rule is that common command-line specified parameters override
file-extracted parameters which override default parameters.

Matrix binary is the default binary format when no keywords specific to
general binary are given, i.e., `array`, `record`, `format`, `filetype`.

General binary data can be entered at the command line via the special file
name '-'.  However, this is intended for use through a pipe where programs
can exchange binary data, not for keyboards.  There is no "end of record"
character for binary data.  Gnuplot continues reading from a pipe until it
has read the number of points declared in the `array` qualifier.

See `datafile binary` for more details.

@menu
* binary::                      
* binary_general::              
* every::                       
* example_datafile::            
* index::                       
* smooth::                      
* special-filenames::           
* thru::                        
* using::                       
@end menu

@node binary, binary_general, data, data
@subsubsection binary

@c ?commands plot datafile binary
@c ?plot datafile binary
@c ?splot datafile binary
@c ?plot binary
@c ?splot binary
@c ?data-file binary
@c ?datafile binary
@cindex binary

The `binary` keyword allows a data file to be binary as opposed to ASCII.
There are two formats for binary--matrix binary and general binary.  Matrix
binary is a fixed format in which data appears in a 2D array with an extra
row and column for coordinate values.  General binary is a flexible format
for which details about the file must be given at the command line.

See `binary matrix` or `binary general` for more details.

@node binary_general, every, binary, data
@subsubsection binary general

@c ?commands plot datafile binary general
@c ?commands splot datafile binary general
@c ?plot binary general
@c ?splot binary general
@c ?binary general
General binary data in which format information is not necessarily part of
the file can be read by giving further details about the file format at the
command line.  Although the syntax is slightly arcane to the casual user,
general binary is particularly useful for application programs using gnuplot
and sending large amounts of data.

Syntax:
@example
      plot '<file_name>' @{binary <binary list>@} ...
      splot '<file_name>' @{binary <binary list>@} ...

@end example

General binary format is activated by keywords in <binary list> pertaining
to information about file structure, i.e., `array`, `record`, `format` or
`filetype`.  Otherwise, matrix binary format is assumed.  (See `binary matrix`
for more details.)

There are some standard file types that may be read for which details about
the binary format may be extracted automatically.  (Type `show datafile
binary` at the command line for a list.)  Otherwise, details must be
specified at the command line or set in the defaults.  Keywords are described
below.

The keyword `filetype` in <binary list> controls the routine used to
read the file, i.e., the format of the data.  For a list of the supported
file types, type `show datafile binary filetypes`.  If no file type is
given, the rule is that traditional gnuplot binary is assumed for `splot`
if the `binary` keyword stands alone.  In all other circumstances, for
`plot` or when one of the <binary list> keywords appears, a raw binary
file is assumed whereby the keywords specify the binary format.

General binary data files fall into two basic classes, and some files may
be of both classes depending upon how they are treated.  There is that
class for which uniform sampling is assumed and point coordinates must be
generated.  This is the class for which full control via the <binary
list> keywords applies.  For this class, the settings precedence is that
command line parameters override in-file parameters, which override
default settings.  The other class is that set of files for which
coordinate information is contained within the file or there is possibly
a non-uniform sampling such as gnuplot binary.

Other than for the unique data files such as gnuplot binary, one should
think of binary data as conceptually the same as ASCII data.  Each point
has columns of information which are selected via the `<using list>`
associated with @ref{using}.  When no `format` string is specified, gnuplot
will retrieve a number of binary variables equal to the largest column
given in the `<using list>`.  For example, `using 1:3` will result in
three columns being read, of which the second will be ignored.  There are
default using lists based upon the typical number of parameters associated
with a certain plot type.  For example, `with image` has a default of
`using 1`, while `with rgbimage` has a default of `using 1:2:3`.  Note
that the special characters for @ref{using} representing point/line/index
generally should not be used for binary data.  There are keywords in
<binary list> that control this.


@noindent --- ARRAY ---

@c ?binary general array
Describes the sampling array dimensions associated with the binary file.
The coordinates will be generated by gnuplot.  A number must be specified
for each dimension, thereby calling out the size of the array.  For example,
`array=10x20` means the underlying sampling structure is two-dimensional with
10 points along the first (x) dimension and 20 points along the second (y)
dimension.  A special "number", `Inf`, can be used to indicate that data should
be read until the end of file.  A colon can be used to separate the dimensions
for multiple records.  For example, `array=25:35` indicates there are two
one-dimensional records within the file.  The colon behavior applies to the
remaining keywords in this list for which it makes sense to be associated with
individual records.

Currently, syntax allows for up to three-dimensional arrays.  However, no
conventions have yet been made for handling three-dimensional coordinates.


@noindent --- RECORD ---

@c ?binary general record
This keyword serves the same function as `array`, having the same syntax.
However, `record` causes gnuplot to not generate coordinate information.
This is for the case where such information may be included in one of the
columns of the binary data file.


@noindent --- FORMAT ---

@c ?binary general format
The default binary format is a float.  For more flexibility, the format can
include details about variable sizes.  For example, `format="%uchar%int%float"`
associates an unsigned character with the first using column, an int with the
second column and a float with the third column.  If the number of size
specifications is less than the greatest column number, the size is implicitly
taken to be similar to the last given variable size.

Furthermore, the format specification can include "discarded" terms via the `*`
character.  For example, to skip the middle column of the previous example, one
could write `format="%uchar%*int%float"` and gnuplot will discard the middle
integer.  To list variable sizes, type `show datafile binary datasizes`.  There
are a group of names that are machine dependent along with their sizes in bytes
for the particular compilation.  There is also a group of names which attempt
to be machine independent.


@noindent --- ENDIAN ---

@c ?binary general endian
Often the endianess of binary data in the file does not agree with the
endianess used by the platform on which gnuplot is running.  Several words can
direct gnuplot how to arrange bytes.  For example `endian=little` means treat
the binary file as having byte significance from least to greatest. The options
are

@example
              little:  least significant to greatest significance
                 big:  greatest significance to least significance
             default:  assume file endianess is the same as compiler
         swap (swab):  Interchange the significance.  (If things
                       don't look right, try this.)

@end example

Gnuplot can support "middle" ("pdp") endian if it is compiled with that option.


@noindent --- FILETYPE ---

@c ?binary general filetype
For some standard binary file formats gnuplot can extract all the necessary
information from the file in question.  As an example, "format=edf" will read
ESRF Header File format files.  For a list of the currently supported file
formats, type `show datafile binary filetypes`.

There is a special file type called `auto` for which gnuplot will check if the
binary file's extension is a quasi-standard extension for a supported format.

Command line keywords may be used to override settings extracted from the file.
The settings from the file override any defaults.  (See `set datafile binary`
for details.)


@noindent --- AVS ---

@c ?binary general filetype avs
@c ?filetype avs
@cindex avs

`avs` is one of the automatically recognized binary file types for images.
AVS is an extremely simple format, suitable mostly for streaming between
applications. It consists of 2 longs (xwidth, ywidth) followed by a stream
of pixels, each with four bytes of information alpha/red/green/blue.


@noindent --- EDF ---

@c ?binary general filetype edf
@c ?filetype edf
@cindex edf

@c ?filetype ehf
@cindex ehf

`edf` is one of the automatically recognized binary file types for images.
EDF stands for ESRF Data Format, and it supports both edf and ehf formats
(the latter means ESRF Header Format).  More information on specifications
can be found at

@example
  http://www.esrf.fr/computing/expg/subgroups/general/format/Format.html

@end example

See also `binary`.


@noindent --- KEYWORDS ---

@c ?binary general keywords
@c ?filetype keywords
The following keywords apply only when generating coordinates.  That is, when
the keyword `array` is used.


@noindent --- SCAN ---

@c ?binary general keywords scan
A great deal of confusion can arise concerning the relationship between how
gnuplot scans a binary file and the dimensions seen on the plot.  To lessen
the confusion, conceptually think of gnuplot _always_ scanning the binary file
point/line/plane or fast/medium/slow.  Then this keyword is used to tell
gnuplot how to map this scanning convention to the Cartesian convention shown
in plots, i.e., x/y/z.  The qualifier for scan is a two or three letter code
representing where point is assigned (first letter), line is assigned (second
letter), and plane is assigned (third letter).  For example, `scan=yx` means
the fastest, point-by-point, increment should be mapped along the Cartesian
y dimension and the middle, line-by-line, increment should be mapped along the
x dimension.

When the plotting mode is `plot`, the qualifier code can include the two
letters x and y.  For `splot`, it can include the three letters x, y and z.

There is nothing restricting the inherent mapping from point/line/plane to
apply only to Cartesian coordinates.  For this reason there are cylindrical
coordinate synonyms for the qualifier codes where t (theta), r and z are
analogous to the x, y and z of Cartesian coordinates.


@noindent --- TRANSPOSE ---

@c ?binary general keywords transpose
Shorthand notation for `scan=yx` or `scan=yxz`.


@noindent --- DX, DY, DZ ---

@c ?binary general keywords dx
When gnuplot generates coordinates, it uses the spacing described by these
keywords.  For example `dx=10 dy=20` would mean space samples along the
x dimension by 10 and space samples along the y dimension by 20.  `dy` cannot
appear if `dx` does not appear.  Similarly, `dz` cannot appear if `dy` does not
appear.  If the underlying dimensions are greater than the keywords specified,
the spacing of the highest dimension given is extended to the other dimensions.
For example, if an image is being read from a file and only `dx=3.5` is given
gnuplot uses a delta x and delta y of 3.5.

The following keywords also apply only when generating coordinates.  However
they may also be used with matrix binary files.


@noindent --- FLIPX, FLIPY, FLIPZ ---

@c ?binary general keywords flipx
Sometimes the scanning directions in a binary datafile are not consistent with
that assumed by gnuplot.  These keywords can flip the scanning direction along
dimensions x, y, z.


@noindent --- ORIGIN  ---

@c ?binary general keywords origin
When gnuplot generates coordinates based upon transposition and flip, it
attempts to always position the lower left point in the array at the origin,
i.e., the data lies in the first quadrant of a Cartesian system after transpose
and flip.

To position the array somewhere else on the graph, the @ref{origin} keyword directs
gnuplot to position the lower left point of the array at a point specified by a
tuple.  The tuple should be a double for `plot` and a triple for `splot`.
For example, `origin=(100,100):(100,200)` is for two records in the file and
intended for plotting in two dimensions. A second example, `origin=(0,0,3.5)`,
is for plotting in three dimensions.


@noindent --- CENTER ---

@c ?binary general keywords center
Similar to @ref{origin}, this keyword will position the array such that its center
lies at the point given by the tuple.  For example, `center=(0,0)`.  Center
does not apply when the size of the array is `Inf`.


@noindent --- ROTATE ---

@c ?binary general keywords rotate
The transpose and flip commands provide some flexibility in generating and
orienting coordinates.  However, for full degrees of freedom, it is possible to
apply a rotational vector described by a rotational angle in two dimensions.

The `rotate` keyword applies to the two-dimensional plane, whether it be `plot`
or `splot`.  The rotation is done with respect to the positive angle of the
Cartesian plane.

The angle can be expressed in radians, radians as a multiple of pi, or degrees.
For example, `rotate=1.5708`, `rotate=0.5pi` and `rotate=90deg` are equivalent.

If @ref{origin} is specified, the rotation is done about the lower left sample
point before translation.  Otherwise, the rotation is done about the array
`center`.


@noindent --- PERPENDICULAR ---

@c ?binary general keywords perpendicular
For `splot`, the concept of a rotational vector is implemented by a triple
representing the vector to be oriented normal to the two-dimensional x-y plane.
Naturally, the default is (0,0,1).  Thus specifying both rotate and
perpendicular together can orient data myriad ways in three-space.

The two-dimensional rotation is done first, followed by the three-dimensional
rotation.  That is, if R' is the rotational 2 x 2 matrix described by an angle,
and P is the 3 x 3 matrix projecting (0,0,1) to (xp,yp,zp), let R be
constructed from R' at the upper left sub-matrix, 1 at element 3,3 and zeros
elsewhere.  Then the matrix formula for translating data is v' = P R v, where v
is the 3 x 1 vector of data extracted from the data file.  In cases where the
data of the file is inherently not three-dimensional, logical rules are used to
place the data in three-space.  (E.g., usually setting the z-dimension value to
zero and placing 2D data in the x-y plane.)


@noindent --- BINARY EXAMPLES ---

@cindex binary_examples

@c ?binary examples
@c ?binary general examples
Examples:

@example
      # Selects two float values (second one implicit) with a float value
      # discarded between them for an indefinite length of 1D data.
      plot '<file_name>' binary format="%float%*float" using 1:2 with lines

@end example

@example
      # The data file header contains all details necessary for creating
      # coordinates from an EDF file.
      plot '<file_name>' binary filetype=edf with image
      plot '<file_name>.edf' binary filetype=auto with image

@end example

@example
      # Selects three unsigned characters for components of a raw RGB image
      # and flips the y-dimension so that typical image orientation (start
      # at top left corner) translates to the Cartesian plane.  Pixel
      # spacing is given and there are two images in the file.  One of them
      # is translated via origin.
      plot '<file_name>' binary array=512x1024:1024x512 format='%uchar' \
           dx=2:1 dy=1:2 origin=(0,0):(1024,1024) flipy u 1:2:3 w rgbimage

@end example

@example
      # Four separate records in which the coordinates are part of the
      # data file.  The file was created with a endianess different from
      # the system on which gnuplot is running.
      splot '<file_name>' binary record=30:30:29:26 endian=swap u 1:2:3

@end example

See also `binary matrix`.

@node every, example_datafile, binary_general, data
@subsubsection every

@c ?commands plot datafile every
@c ?plot datafile every
@c ?plot every
@c ?data-file every
@c ?datafile every
@cindex every

The @ref{every} keyword allows a periodic sampling of a data set to be plotted.

In the discussion a "point" is a datum defined by a single record in the
file; "block" here will mean the same thing as "datablock" (see `glossary`).

Syntax:
@example
      plot 'file' every @{<point_incr>@}
                          @{:@{<block_incr>@}
                            @{:@{<start_point>@}
                              @{:@{<start_block>@}
                                @{:@{<end_point>@}
                                  @{:<end_block>@}@}@}@}@}

@end example

The data points to be plotted are selected according to a loop from
<`start_point`> to <`end_point`> with increment <`point_incr`> and the
blocks according to a loop from <`start_block`> to <`end_block`> with
increment <`block_incr`>.

The first datum in each block is numbered '0', as is the first block in the
file.

Note that records containing unplottable information are counted.

Any of the numbers can be omitted; the increments default to unity, the start
values to the first point or block, and the end values to the last point or
block.  If @ref{every} is not specified, all points in all lines are plotted.

Examples:
@example
      every :::3::3    # selects just the fourth block ('0' is first)
      every :::::9     # selects the first 10 blocks
      every 2:2        # selects every other point in every other block
      every ::5::15    # selects points 5 through 15 in each block

@end example

See
@uref{http://www.gnuplot.info/demo/simple.html,simple plot demos (simple.dem)
}
,
@uref{http://www.gnuplot.info/demo/surface1.html,Non-parametric splot demos
}
, and
@uref{http://gnuplot.sourceforge.net/demo/surface2.html,Parametric splot demos
}
.

@node example_datafile, index, every, data
@subsubsection example datafile

@c ?commands plot datafile example
@c ?plot datafile example
@c ?plot example
@c ?datafile example
@c ?data-file example
@cindex example

This example plots the data in the file "population.dat" and a theoretical
curve:

@example
      pop(x) = 103*exp((1965-x)/10)
      plot [1960:1990] 'population.dat', pop(x)

@end example

The file "population.dat" might contain:

@example
      # Gnu population in Antarctica since 1965
         1965   103
         1970   55
         1975   34
         1980   24
         1985   10

@end example

@c ^ <img align=bottom src="http://www.gnuplot.info/doc/population.gif" alt="[population.gif]" width=640 height=480>

@node index, smooth, example_datafile, data
@subsubsection index

@c ?commands plot datafile index
@c ?plot datafile index
@c ?plot index
@c ?data-file index
@c ?datafile index
@cindex index

The @ref{index} keyword allows you to select specific data sets in a multi-data-set
file for plotting.

Syntax:
@example
      plot 'file' index <m>@{@{:<n>@}:<p>@}

@end example

Data sets are separated by pairs of blank records.  `index <m>` selects only
set <m>; `index <m>:<n>` selects sets in the range <m> to <n>; and `index
<m>:<n>:<p>` selects indices <m>, <m>+<p>, <m>+2<p>, etc., but stopping at
<n>.  Following C indexing, the index 0 is assigned to the first data set in
the file.  Specifying too large an index results in an error message.  If
@ref{index} is not specified, all sets are plotted as a single data set.

Example:
@example
      plot 'file' index 4:5

@end example

For each point in the file, the index value of the data set it appears in is
available via the pseudo-column `column(-2)`.  This leads to an alternative way
of distinguishing individual data sets within a file as shown below.  This is
more awkward that the @ref{index} command if all you are doing is selecting one
data set for plotting, but is very useful if you want to assign different
properties to each data set.  See `lc variable`.

Example:
@example
      plot 'file' using 1:(column(-2)==4 ? $2 : NaN)        # very awkward
      plot 'file' using 1:2:(column(-2)) linecolor variable # very useful!

@end example

@c ^ See also web page
@uref{http://www.gnuplot.info/demo/multimsh.html, splot with indices demo.
}

@node smooth, special-filenames, index, data
@subsubsection smooth

@c ?commands plot datafile smooth
@c ?plot datafile smooth
@c ?plot smooth
@c ?data-file smooth
@c ?datafile smooth
@cindex smooth

`gnuplot` includes a few general-purpose routines for interpolation and
approximation of data; these are grouped under the @ref{smooth} option.  More
sophisticated data processing may be performed by preprocessing the data
externally or by using @ref{fit} with an appropriate model.

Syntax:
@example
      smooth @{unique | frequency | csplines | acsplines | bezier | sbezier@}

@end example

`unique` and `frequency` plot the data after making them monotonic.  Each of
the other routines uses the data to determine the coefficients of a
continuous curve between the endpoints of the data.  This curve is then
plotted in the same manner as a function, that is, by finding its value at
uniform intervals along the abscissa (see @ref{samples}) and connecting these
points with straight line segments (if a line style is chosen).

If @ref{autoscale} is in effect, the ranges will be computed such that the
plotted curve lies within the borders of the graph.

If @ref{autoscale} is not in effect, and the smooth option is either `acspline`
or `cspline`, the sampling of the generated curve is
done across the intersection of the x range covered by the input data and
the fixed abscissa range as defined by @ref{xrange}.

If too few points are available to allow the selected option to be applied,
an error message is produced.  The minimum number is one for `unique` and
`frequency`, four for `acsplines`, and three for the others.

The @ref{smooth} options have no effect on function plots.


@noindent --- ACSPLINES ---

@c ?commands plot datafile smooth acsplines
@c ?plot datafile smooth acsplines
@c ?data-file smooth acsplines
@c ?datafile smooth acsplines
@c ?plot smooth acsplines
@c ?plot acsplines
@c ?smooth acsplines
@cindex acsplines

The `acsplines` option approximates the data with a "natural smoothing spline".
After the data are made monotonic in x (see `smooth unique`), a curve is
piecewise constructed from segments of cubic polynomials whose coefficients
are found by the weighting the data points; the weights are taken from the
third column in the data file.  That default can be modified by the third
entry in the @ref{using} list, e.g.,
@example
      plot 'data-file' using 1:2:(1.0) smooth acsplines

@end example

Qualitatively, the absolute magnitude of the weights determines the number
of segments used to construct the curve.  If the weights are large, the
effect of each datum is large and the curve approaches that produced by
connecting consecutive points with natural cubic splines.  If the weights are
small, the curve is composed of fewer segments and thus is smoother; the
limiting case is the single segment produced by a weighted linear least
squares fit to all the data.  The smoothing weight can be expressed in terms
of errors as a statistical weight for a point divided by a "smoothing factor"
for the curve so that (standard) errors in the file can be used as smoothing
weights.

Example:
@example
      sw(x,S)=1/(x*x*S)
      plot 'data_file' using 1:2:(sw($3,100)) smooth acsplines

@end example


@noindent --- BEZIER ---

@c ?commands plot datafile smooth bezier
@c ?plot datafile smooth bezier
@c ?plot smooth bezier
@c ?data-file smooth bezier
@c ?datafile smooth bezier
@c ?plot bezier
@c ?smooth bezier
@cindex bezier

The `bezier` option approximates the data with a Bezier curve of degree n
(the number of data points) that connects the endpoints.


@noindent --- CSPLINES ---

@c ?commands plot datafile smooth csplines
@c ?plot datafile smooth csplines
@c ?plot smooth csplines
@c ?data-file smooth csplines
@c ?datafile smooth csplines
@c ?plot csplines
@c ?smooth csplines
@cindex csplines

The `csplines` option connects consecutive points by natural cubic splines
after rendering the data monotonic (see `smooth unique`).


@noindent --- SBEZIER ---

@c ?commands plot datafile smooth sbezier
@c ?plot datafile smooth sbezier
@c ?plot smooth sbezier
@c ?data-file smooth sbezier
@c ?datafile smooth sbezier
@c ?plot sbezier
@c ?smooth sbezier
@cindex sbezier

The `sbezier` option first renders the data monotonic (`unique`) and then
applies the `bezier` algorithm.


@noindent --- UNIQUE ---

@c ?commands plot datafile smooth unique
@c ?plot datafile smooth unique
@c ?plot smooth unique
@c ?data-file smooth unique
@c ?datafile smooth unique
@c ?plot unique
@c ?smooth unique
@cindex unique

The `unique` option makes the data monotonic in x; points with the same
x-value are replaced by a single point having the average y-value.  The
resulting points are then connected by straight line segments.
@c ^ See this
@uref{http://www.gnuplot.info/demo/mgr.html,demos
}
@c ^ web page.


@noindent --- FREQUENCY ---

@c ?commands plot datafile smooth frequency
@c ?plot datafile smooth frequency
@c ?plot smooth frequency
@c ?data-file smooth frequency
@c ?datafile smooth frequency
@c ?plot frequency
@c ?smooth frequency
@cindex frequency

The `frequency` option makes the data monotonic in x; points with the same
x-value are replaced by a single point having the summed y-values.  The
resulting points are then connected by straight line segments.

@node special-filenames, thru, smooth, data
@subsubsection special-filenames

@c ?commands plot datafile special-filenames
@c ?plot datafile special-filenames
@c ?plot special-filenames
@c ?datafile special-filenames
@cindex special-filenames

A special filename of `'-'` specifies that the data are inline; i.e., they
follow the command.  Only the data follow the command; `plot` options like
filters, titles, and line styles remain on the `plot` command line.  This is
similar to << in unix shell script, and $DECK in VMS DCL.  The data are
entered as though they are being read from a file, one data point per record.
The letter "e" at the start of the first column terminates data entry.  The
@ref{using} option can be applied to these data---using it to filter them through
a function might make sense, but selecting columns probably doesn't!

`'-'` is intended for situations where it is useful to have data and commands
together, e.g., when `gnuplot` is run as a sub-process of some front-end
application.  Some of the demos, for example, might use this feature.  While
`plot` options such as @ref{index} and @ref{every} are recognized, their use forces
you to enter data that won't be used.  For example, while

@example
      plot '-' index 0, '-' index 1
      2
      4
      6

@end example


@example
      10
      12
      14
      e
      2
      4
      6

@end example


@example
      10
      12
      14
      e

@end example

does indeed work,

@example
      plot '-', '-'
      2
      4
      6
      e
      10
      12
      14
      e

@end example

is a lot easier to type.

If you use `'-'` with @ref{replot}, you may need to enter the data more than once
(see @ref{replot}).

A blank filename ('') specifies that the previous filename should be reused.
This can be useful with things like

@example
      plot 'a/very/long/filename' using 1:2, '' using 1:3, '' using 1:4

@end example

(If you use both `'-'` and `''` on the same `plot` command, you'll need to
have two sets of inline data, as in the example above.)

On some computer systems with a popen function (Unix), the datafile can be
piped through a shell command by starting the file name with a '<'.  For
example,

@example
      pop(x) = 103*exp(-x/10)
      plot "< awk '@{print $1-1965, $2@}' population.dat", pop(x)

@end example

would plot the same information as the first population example but with
years since 1965 as the x axis.  If you want to execute this example, you
have to delete all comments from the data file above or substitute the
following command for the first part of the command above (the part up to
the comma):

@example
      plot "< awk '$0 !~ /^#/ @{print $1-1965, $2@}' population.dat"

@end example

While this approach is most flexible, it is possible to achieve simple
filtering with the @ref{using} or @ref{thru} keywords.

@node thru, using, special-filenames, data
@subsubsection thru

@c ?commands plot datafile thru
@c ?plot datafile thru
@c ?plot thru
@c ?data-file thru
@c ?datafile thru
@cindex thru

The @ref{thru} function is provided for backward compatibility.

Syntax:
@example
      plot 'file' thru f(x)

@end example

It is equivalent to:

@example
      plot 'file' using 1:(f($2))

@end example

While the latter appears more complex, it is much more flexible.  The more
natural

@example
      plot 'file' thru f(y)

@end example

also works (i.e. you can use y as the dummy variable).

@ref{thru} is parsed for `splot` and @ref{fit} but has no effect.

@node using,  , thru, data
@subsubsection using

@c ?commands plot datafile using
@c ?plot datafile using
@c ?plot using
@c ?data-file using
@c ?datafile using
@cindex using

The most common datafile modifier is @ref{using}.

Syntax:
@example
      plot 'file' using @{<entry> @{:<entry> @{:<entry> ...@}@}@} @{'format'@}

@end example

If a format is specified, each datafile record is read using the C library's
'scanf' function, with the specified format string.  Otherwise the record is
read and broken into columns. By default the separation between columns is
whitespace (spaces and/or tabs), but see `datafile separator`.

Each <entry> may be a simple column number that selects the value from one
field of the input fit, an expression enclosed in parentheses, or empty.

If the entry is an expression in parentheses, then the function column(N) may
be used to indicate the value in column N. That is, column(1) refers to the
first item read, column(2) to the second, and so on.  The special symbols
$1, $2, ... are shorthand for column(1), column(2) ...  The function `valid(N)`
tests whether the value in the Nth column is a valid number.

In addition to the actual columns 1...N in the input data file, gnuplot
presents data from several "pseudo-columns" that hold bookkeeping information.
E.g. $0 or column(0) returns the sequence number of this data record within a
dataset.

An empty <entry> will default to its order in the list of entries.
For example, `using ::4` is interpreted as `using 1:2:4`.

If the @ref{using} list has but a single entry, that <entry> will be used for y
and the data point number (pseudo-column $0) is used for x; for example,
"`plot 'file' using 1`" is identical to "`plot 'file' using 0:1`".
If the @ref{using} list has two entries, these will be used for x and y.
See @ref{style} and @ref{fit} for details about plotting styles that make use of
data from additional columns of input.

'scanf' accepts several numerical specifications but `gnuplot`
requires all inputs to be double-precision floating-point variables,
so "%lf" is essentially the only permissible specifier.
A format string given by the user must contain at least one such
input specifier, and no more than seven of them.
'scanf' expects to see white space---a blank, tab
("\t"), newline ("\n"), or formfeed ("\f")---between numbers; anything else
in the input stream must be explicitly skipped.

Note that the use of "\t", "\n", or "\f" requires use of double-quotes
rather than single-quotes.


@noindent --- USING_EXAMPLES ---

@cindex examples

@c ?commands plot datafile using examples
@c ?plot datafile using examples
@c ?datafile using examples
@c ?using examples
This creates a plot of the sum of the 2nd and 3rd data against the first:
The format string specifies comma- rather than space-separated columns.
The same result could be achieved by specifying `set datafile separator ","`.
@example
      plot 'file' using 1:($2+$3) '%lf,%lf,%lf'

@end example

In this example the data are read from the file "MyData" using a more
complicated format:
@example
      plot 'MyData' using "%*lf%lf%*20[^\n]%lf"

@end example

The meaning of this format is:

@example
      %*lf        ignore a number
      %lf         read a double-precision number (x by default)
      %*20[^\n]   ignore 20 non-newline characters
      %lf         read a double-precision number (y by default)

@end example

One trick is to use the ternary `?:` operator to filter data:

@example
      plot 'file' using 1:($3>10 ? $2 : 1/0)

@end example

which plots the datum in column two against that in column one provided
the datum in column three exceeds ten.  `1/0` is undefined; `gnuplot`
quietly ignores undefined points, so unsuitable points are suppressed.
Or you can use the pre-defined variable NaN to achieve the same result.
@cindex NaN


In fact, you can use a constant expression for the column number, provided it
doesn't start with an opening parenthesis; constructs like `using
0+(complicated expression)` can be used.  The crucial point is that the
expression is evaluated once if it doesn't start with a left parenthesis, or
once for each data point read if it does.

If timeseries data are being used, the time can span multiple columns.  The
starting column should be specified.  Note that the spaces within the time
must be included when calculating starting columns for other data.  E.g., if
the first element on a line is a time with an embedded space, the y value
should be specified as column three.

It should be noted that `plot 'file'`, `plot 'file' using 1:2`, and `plot
'file' using ($1):($2)` can be subtly different: 1) if @ref{file} has some lines
with one column and some with two, the first will invent x values when they
are missing, the second will quietly ignore the lines with one column, and
the third will store an undefined value for lines with one point (so that in
a plot with lines, no line joins points across the bad point); 2) if a line
contains text at the first column, the first will abort the plot on an error,
but the second and third should quietly skip the garbage.

In fact, it is often possible to plot a file with lots of lines of garbage at
the top simply by specifying

@example
      plot 'file' using 1:2

@end example

However, if you want to leave text in your data files, it is safer to put the
comment character (#) in the first column of the text lines.
@c ^ See also the web page
@uref{http://www.gnuplot.info/demo/using.html,Feeble using demos.
}

If gnuplot is built with configuration option --enable-datastrings, then
additional modifiers to @ref{using} can specify handling of text fields in the
datafile. See `datastrings`, `using xticlabels`, @ref{title}.


@noindent --- USING TITLE ---

@c ?using title
@c ?plot using title
If gnuplot is built with configuration option --enable-datastrings, then
the first entry of a column of the input data file can be used as a string
to provide the plot title in the key box.  The column containing specified
is independent of the column[s] used for the plot itself.

@example
   plot 'data' using 1:($2/$3) title column(N)

@end example

In this case the entry in the first row of column N will be used for the
key entry of the plot constructed from dividing column 2 by column 3.
The entry in the first row of columns 2 and 3 will be ignored.



@noindent --- XTICLABELS ---

@c ?using xticlabels
@c ?plot using xticlabels
If gnuplot is built with configuration option --enable-datastrings, then
a column of the input data file can be used to label axis tic marks.
The format of such a plot command is

@example
  plot 'datafile' using <xcol>:<ycol>:xticlabels(<labelcol>) with <plotstyle>

@end example

Tic labels may be read for any of the plot axes: x x2 y y2 z.
The `ticlabels(<labelcol>)` specifiers must come after all of the data
coordinate specifiers in the @ref{using} portion of the command.
For each data point which has a valid set of X,Y[,Z] coordinates,
the text field found in column <labelcol> is added to the list of xtic labels
at the same X coordinate as the point it belongs to. `xticlabels(<labelcol>)`
may be shortened to `xtic(<labelcol>)`.

Example:

@example
      splot "data" using 2:4:6:xtic(1):ytic(3):ztic(6)

@end example

In this example the x and y axis tic labels are taken from different columns
than the x and y coordinate values. The z axis tics, however, are generated
from the z coordinate of the corresponding point.


@noindent --- X2TICLABELS ---

@c ?using x2ticlabels
@c ?plot using x2ticlabels
See `plot using xticlabels`.


@noindent --- YTICLABELS ---

@c ?using yticlabels
@c ?plot using yticlabels
See `plot using xticlabels`.


@noindent --- Y2TICLABELS ---

@c ?using y2ticlabels
@c ?plot using y2ticlabels
See `plot using xticlabels`.


@noindent --- ZTICLABELS ---

@c ?using zticlabels
@c ?plot using zticlabels
See `plot using xticlabels`.

@node errorbars, errorlines, data, plot
@subsection errorbars

@c ?commands plot errorbars
@c ?commands splot errorbars
@c ?plot errorbars
@c ?splot errorbars
@cindex errorbars

Error bars are supported for 2-d data file plots by reading one to four
additional columns (or @ref{using} entries); these additional values are used in
different ways by the various errorbar styles.

In the default situation, `gnuplot` expects to see three, four, or six
numbers on each line of the data file---either

@example
      (x, y, ydelta),
      (x, y, ylow, yhigh),
      (x, y, xdelta),
      (x, y, xlow, xhigh),
      (x, y, xdelta, ydelta), or
      (x, y, xlow, xhigh, ylow, yhigh).

@end example

The x coordinate must be specified.  The order of the numbers must be
exactly as given above, though the @ref{using} qualifier can manipulate the order
and provide values for missing columns.  For example,

@example
      plot 'file' with errorbars
      plot 'file' using 1:2:(sqrt($1)) with xerrorbars
      plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars

@end example

The last example is for a file containing an unsupported combination of
relative x and absolute y errors.  The @ref{using} entry generates absolute x min
and max from the relative error.

The y error bar is a vertical line plotted from (x, ylow) to (x,
yhigh). If ydelta is specified instead of ylow and yhigh, ylow = y -
ydelta and yhigh = y + ydelta are derived. If there are only two
numbers on the record, yhigh and ylow are both set to y. The x error
bar is a horizontal line computed in the same fashion. To get lines
plotted between the data points, `plot` the data file twice, once with
errorbars and once with lines (but remember to use the `notitle`
option on one to avoid two entries in the key). Alternately, use the
errorlines command (see @ref{errorlines}).

The error bars have crossbars at each end unless @ref{bars} is used
(see @ref{bars} for details).

If autoscaling is on, the ranges will be adjusted to include the error bars.

See also
@uref{http://gnuplot.sourceforge.net/demo/mgr.html,errorbar demos.
}

See @ref{using}, @ref{with}, and @ref{style} for more information.

@node errorlines, parametric, errorbars, plot
@subsection errorlines

@c ?commands plot errorlines
@c ?commands splot errorlines
@c ?plot errorlines
@c ?splot errorlines
@cindex errorlines

Lines with error bars are supported for 2-d data file plots by reading
one to four additional columns (or @ref{using} entries); these additional
values are used in different ways by the various errorlines styles.

In the default situation, `gnuplot` expects to see three, four, or six
numbers on each line of the data file---either

@example
      (x, y, ydelta),
      (x, y, ylow, yhigh),
      (x, y, xdelta),
      (x, y, xlow, xhigh),
      (x, y, xdelta, ydelta), or
      (x, y, xlow, xhigh, ylow, yhigh).

@end example

The x coordinate must be specified. The order of the numbers must be
exactly as given above, though the @ref{using} qualifier can manipulate
the order and provide values for missing columns. For example,

@example
      plot 'file' with errorlines
      plot 'file' using 1:2:(sqrt($1)) with xerrorlines
      plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorlines

@end example

The last example is for a file containing an unsupported combination
of relative x and absolute y errors. The @ref{using} entry generates
absolute x min and max from the relative error.

The y error bar is a vertical line plotted from (x, ylow) to (x,
yhigh). If ydelta is specified instead of ylow and yhigh, ylow = y -
ydelta and yhigh = y + ydelta are derived. If there are only two
numbers on the record, yhigh and ylow are both set to y. The x error
bar is a horizontal line computed in the same fashion.

The error bars have crossbars at each end unless @ref{bars} is used
(see @ref{bars} for details).

If autoscaling is on, the ranges will be adjusted to include the error bars.

See @ref{using}, @ref{with}, and @ref{style} for more information.

@node parametric, ranges, errorlines, plot
@subsection parametric

@c ?commands plot parametric
@c ?commands splot parametric
@c ?plot parametric
@c ?splot parametric
When in parametric mode (`set parametric`) mathematical expressions must be
given in pairs for `plot` and in triplets for `splot`.

Examples:
@example
      plot sin(t),t**2
      splot cos(u)*cos(v),cos(u)*sin(v),sin(u)

@end example

Data files are plotted as before, except any preceding parametric function
must be fully specified before a data file is given as a plot.  In other
words, the x parametric function (`sin(t)` above) and the y parametric
function (`t**2` above) must not be interrupted with any modifiers or data
functions; doing so will generate a syntax error stating that the parametric
function is not fully specified.

Other modifiers, such as @ref{with} and @ref{title}, may be specified only after the
parametric function has been completed:

@example
      plot sin(t),t**2 title 'Parametric example' with linespoints

@end example

See also
@uref{http://www.gnuplot.info/demo/param.html,Parametric Mode Demos.
}

@node ranges, title, parametric, plot
@subsection ranges

@c ?commands plot ranges
@c ?commands splot ranges
@c ?plot ranges
@c ?splot ranges
@cindex ranges

The optional ranges specify the region of the graph that will be displayed.

Syntax:
@example
      [@{<dummy-var>=@}@{@{<min>@}:@{<max>@}@}]
      [@{@{<min>@}:@{<max>@}@}]

@end example

The first form applies to the independent variable (@ref{xrange} or @ref{trange}, if
in parametric mode).  The second form applies to the dependent variable
@ref{yrange} (and @ref{xrange}, too, if in parametric mode).  <dummy-var> is a new
name for the independent variable.  (The defaults may be changed with @ref{dummy}.)  The optional <min> and <max> terms can be constant expressions or *.

In non-parametric mode, the order in which ranges must be given is @ref{xrange}
and @ref{yrange}.

In parametric mode, the order for the `plot` command is @ref{trange}, @ref{xrange},
and @ref{yrange}.  The following `plot` command shows setting the @ref{trange} to
[-pi:pi], the @ref{xrange} to [-1.3:1.3] and the @ref{yrange} to [-1:1] for the
duration of the graph:

@example
      plot [-pi:pi] [-1.3:1.3] [-1:1] sin(t),t**2

@end example

Note that the x2range and y2range cannot be specified here---@ref{x2range}
and @ref{y2range} must be used.

Ranges are interpreted in the order listed above for the appropriate mode.
Once all those needed are specified, no further ones must be listed, but
unneeded ones cannot be skipped---use an empty range `[]` as a placeholder.

`*` can be used to allow autoscaling of either of min and max.  See also
@ref{autoscale}.

Ranges specified on the `plot` or `splot` command line affect only that
graph; use the @ref{xrange}, @ref{yrange}, etc., commands to change the
default ranges for future graphs.

With time data, you must provide the range (in the same manner as the time
appears in the datafile) within quotes.  `gnuplot` uses the @ref{timefmt} string
to read the value---see @ref{timefmt}.

Examples:

This uses the current ranges:
@example
      plot cos(x)

@end example

This sets the x range only:
@example
      plot [-10:30] sin(pi*x)/(pi*x)

@end example

This is the same, but uses t as the dummy-variable:
@example
      plot [t = -10 :30]  sin(pi*t)/(pi*t)

@end example

This sets both the x and y ranges:
@example
      plot [-pi:pi] [-3:3]  tan(x), 1/x

@end example

This sets only the y range, and turns off autoscaling on both axes:
@example
      plot [ ] [-2:sin(5)*-8] sin(x)**besj0(x)

@end example

This sets xmax and ymin only:
@example
      plot [:200] [-pi:]  exp(sin(x))

@end example

This sets the x range for a timeseries:
@example
      set timefmt "%d/%m/%y %H:%M"
      plot ["1/6/93 12:00":"5/6/93 12:00"] 'timedata.dat'

@end example


@node title, with, ranges, plot
@subsection title

@c ?commands plot title
@c ?commands splot title
@c ?plot title
@c ?splot title
A line title for each function and data set appears in the key, accompanied
by a sample of the line and/or symbol used to represent it.  It can be
changed by using the @ref{title} option.

Syntax:
@example
      title "<title>" | notitle ["<ignored title>"]

@end example

where <title> is the new title of the line and must be enclosed in quotes.
The quotes will not be shown in the key.  A special character may be given as
a backslash followed by its octal value ("\345").  The tab character "\t" is
understood.  Note that backslash processing occurs only for strings enclosed
in double quotes---use single quotes to prevent such processing.  The newline
character "\n" is not processed in key entries in either type of string.

The line title and sample can be omitted from the key by using the keyword
`notitle`.  A null title (`title ''`) is equivalent to `notitle`.  If only
the sample is wanted, use one or more blanks (`title ' '`).  If `notitle`
is followed by a string this string is ignored.

If `key autotitles` is set (which is the default) and neither @ref{title} nor
`notitle` are specified the line title is the function name or the file name as
it appears on the `plot` command.  If it is a file name, any datafile modifiers
specified will be included in the default title.

The layout of the key itself (position, title justification, etc.) can be
controlled by @ref{key}.  Please see @ref{key} for details.

Examples:

This plots y=x with the title 'x':
@example
      plot x

@end example

This plots x squared with title "x^2" and file "data.1" with title
"measured data":
@example
      plot x**2 title "x^2", 'data.1' t "measured data"

@end example

This puts an untitled circular border around a polar graph:
@example
      set polar; plot my_function(t), 1 notitle

@end example

@node with,  , title, plot
@subsection with

@c ?commands plot with
@c ?commands splot with
@c ?commands plot style
@c ?commands splot style
@c ?plot with
@c ?plot style
@c ?splot with
@c ?splot style
@cindex style
@opindex style


@cindex with

Functions and data may be displayed in one of a large number of styles.
The @ref{with} keyword provides the means of selection.

Syntax:
@example
      with <style> @{ @{linestyle | ls <line_style>@}
                     | @{@{linetype  | lt <line_type>@}
                        @{linewidth | lw <line_width>@}
                        @{linecolor | lc <colorspec>@}
                        @{pointtype | pt <point_type>@}
                        @{pointsize | ps <point_size>@}
                        @{fill | fs <fillstyle>@}
                        @{nohidden3d | nocontours@}
                        @{palette@}@}
                   @}

@end example

where <style> is either `lines`, `points`, `linespoints`, `impulses`,
`dots`, `steps`, `fsteps`, `histeps`, @ref{errorbars}, `labels`, `xerrorbars`,
`yerrorbars`, `xyerrorbars`, @ref{errorlines}, `xerrorlines`, `yerrorlines`,
`xyerrorlines`, `boxes`, `histograms`, `filledcurves`, `boxerrorbars`,
`boxxyerrorbars`, `financebars`, `candlesticks`, `vectors`, `image`,
`rgbimage` or @ref{pm3d}. Some of these styles require additional information.
See `plotting styles` for details of each style.  `fill` is relevant only
to certain 2D plots (currently `boxes` `boxxyerrorbars` and `candlesticks`).
Note that `filledcurves` and @ref{pm3d} can take an additional option not
listed above (the latter only when used in the `splot` command)---see
their help or examples below for more details.

Default styles are chosen with the `set style function` and `set style data`
commands.

By default, each function and data file will use a different line type and
point type, up to the maximum number of available types.  All terminal
drivers support at least six different point types, and re-use them, in
order, if more are required.  The LaTeX driver supplies an additional six
point types (all variants of a circle), and thus will only repeat after 12
curves are plotted with points.  The PostScript drivers (@ref{postscript})
supplies a total of 64.

If you wish to choose the line or point type for a single plot, <line_type>
and <point_type> may be specified.  These are positive integer constants (or
expressions) that specify the line type and point type to be used for the
plot.  Use @ref{test} to display the types available for your terminal.

You may also scale the line width and point size for a plot by using
<line_width> and <point_size>, which are specified relative to the default
values for each terminal.  The pointsize may also be altered
globally---see @ref{pointsize} for details.  But note that both <point_size>
as set here and  as set by @ref{pointsize} multiply the default point
size---their effects are  not cumulative.  That is,
`set pointsize 2; plot x w p ps 3` will use points three times default size,
not six.

It is also possible to specify `pointsize variable` either as part of a
line style or for an individual plot. In this case one extra column of input
is required, i.e. 3 columns for a 2D plot and 4 columns for a 3D splot. The
size of each individual point is determined by multiplying the global
pointsize by the value read from the data file.

If you have defined specific line type/width and point type/size combinations
with `set style line`, one of these may be selected by setting <line_style> to
the index of the desired style.

If gnuplot was built with @ref{pm3d} support, the special keyword @ref{palette} is
allowed for smooth color change of lines, points and dots in `splots`. The
color is chosen from a smooth palette which was set previously with the
command @ref{palette}. The color value corresponds to the z-value of the
point coordinates or to the color coordinate if specified by the 4th parameter
in @ref{using}. Both 2d and 3d plots (`plot` and `splot` commands) can use palette
colors as specified by either their fractional value or the corresponding value
mapped to the colorbox range. A palette color value can also be read from an
explicitly specified column in the @ref{using} specifier.
Z value. See `colors`, @ref{palette}, `linetype`.

The keyword `nohidden3d` applies only to plots made with the `splot` command.
Normally the global option @ref{hidden3d} applies to all plots in the graph.
You can attach the `nohidden3d` option to any individual plots that you want
to exclude from the hidden3d processing.  The individual elements other than
surfaces (i.e. lines, dots, labels, ...) of a plot marked `nohidden3d` will all
be drawn, even if they would normally be obscured by other plot elements.

Similarly, the keyword `nocontours` will turn off contouring for an individual
plot even if the global property "set contour" is active.

The keywords may be abbreviated as indicated.

Note that the `linewidth`, @ref{pointsize} and @ref{palette} options are not supported
by all terminals.

Examples:

This plots sin(x) with impulses:
@example
      plot sin(x) with impulses

@end example

This plots x with points, x**2 with the default:
@example
      plot x w points, x**2

@end example

This plots tan(x) with the default function style, file "data.1" with lines:
@example
      plot [ ] [-2:5] tan(x), 'data.1' with l

@end example

This plots "leastsq.dat" with impulses:
@example
      plot 'leastsq.dat' w i

@end example

This plots the data file "population" with boxes:
@example
      plot 'population' with boxes

@end example

This plots "exper.dat" with errorbars and lines connecting the points
(errorbars require three or four columns):
@example
      plot 'exper.dat' w lines, 'exper.dat' notitle w errorbars

@end example

Another way to plot "exper.dat" with errorlines (errorbars require three
or four columns):
@example
      plot 'exper.dat' w errorlines

@end example

This plots sin(x) and cos(x) with linespoints, using the same line type but
different point types:
@example
      plot sin(x) with linesp lt 1 pt 3, cos(x) with linesp lt 1 pt 4

@end example

This plots file "data" with points of type 3 and twice usual size:
@example
      plot 'data' with points pointtype 3 pointsize 2

@end example

This plots file "data" with variable pointsize read from column 4
@example
      plot 'data' using 1:2:4 with points pt 5 pointsize variable

@end example

This plots two data sets with lines differing only by weight:
@example
      plot 'd1' t "good" w l lt 2 lw 3, 'd2' t "bad" w l lt 2 lw 1

@end example

This plots filled curve of x*x and a color stripe:
@example
      plot x*x with filledcurve closed, 40 with filledcurve y1=10

@end example

This plots x*x and a color box:
@example
      plot x*x, (x>=-5 && x<=5 ? 40 : 1/0) with filledcurve y1=10 lt 8

@end example

This plots a surface with color lines:
@example
      splot x*x-y*y with line palette

@end example

This plots two color surfaces at different altitudes:
@example
      splot x*x-y*y with pm3d, x*x+y*y with pm3d at t

@end example


@node print, pwd, plot, Commands
@section print

@c ?commands print
@cindex print
@cmindex print


The @ref{print} command prints the value of <expression> to the screen.  It is
synonymous with `pause 0`.  <expression> may be anything that `gnuplot` can
evaluate that produces a number, or it can be a string.

Syntax:
@example
      print <expression> @{, <expression>, ...@}

@end example

See `expressions`.  The output file can be set with @ref{print}.

@node pwd, quit, print, Commands
@section pwd

@c ?commands pwd
@cindex pwd
@cmindex pwd


The @ref{pwd} command prints the name of the working directory to the screen.

@node quit, raise, pwd, Commands
@section quit

@c ?commands quit
@cindex quit
@cmindex quit


The @ref{exit} and @ref{quit} commands and END-OF-FILE character will exit `gnuplot`.
Each of these commands will clear the output device (as does the @ref{clear}
command) before exiting.

@node raise, replot, quit, Commands
@section raise

@c ?commands raise
@cindex raise
@cmindex raise


Syntax:
@example
      raise @{plot_window_nb@}

@end example

The @ref{raise} command raises (opposite to @ref{lower}) plot window(s) associated
with the interactive terminal of your gnuplot session, i.e. `pm`, `win`, `wxt`
or `x11`. It puts the plot window to front (top) in the z-order windows stack
of the window manager of your desktop.

As `x11` and `wxt` support multiple plot windows, then by default they raise
these windows in descending order of most recently created on top to the least
recently created on bottom. If a plot number is supplied as an optional
parameter, only the associated plot window will be raised if it exists.

The optional parameter is ignored for single plot-windows terminal, i.e. `pm`
and `win`.

@example
 If the window is not raised under X11, then (1) they don't run in the same
 X11 session (telnet or ssh session, for example), or (2) raising is blocked
 by your window manager. On KDE, you may like to go to the KDE Control Center
 => Desktop => Window Behaviour => Advanced and set the "Focus stealing
 prevention level" to None (default is Low).

@end example

@node replot, reread, raise, Commands
@section replot

@c ?commands replot
@cindex replot
@cmindex replot


The @ref{replot} command without arguments repeats the last `plot` or `splot`
command.  This can be useful for viewing a plot with different `set` options,
or when generating the same plot for several devices.

Arguments specified after a @ref{replot} command will be added onto the last
`plot` or `splot` command (with an implied ',' separator) before it is
repeated.  @ref{replot} accepts the same arguments as the `plot` and `splot`
commands except that ranges cannot be specified.  Thus you can use @ref{replot}
to plot a function against the second axes if the previous command was `plot`
but not if it was `splot`.

N.B.---use of

@example
      plot '-' ; ... ; replot

@end example

is not recommended.  `gnuplot` does not store the inline data internally, so
since @ref{replot} appends new information to the previous `plot` and then
executes the modified command, the `'-'` from the initial `plot` will expect
to read inline data again.

Note that @ref{replot} does not work in @ref{multiplot} mode, since it reproduces
only the last plot rather than the entire screen.

See also `command-line-editing` for ways to edit the last `plot` (`splot`)
command.

See also `show plot` to show the whole current plotting command, and the
possibility to copy it into the `history`.

@node reread, reset, replot, Commands
@section reread

@c ?commands reread
@cindex reread
@cmindex reread


The @ref{reread} command causes the current `gnuplot` command file, as specified
by a `load` command or on the command line, to be reset to its starting
point before further commands are read from it.  This essentially implements
an endless loop of the commands from the beginning of the command file to
the @ref{reread} command.  (But this is not necessarily a disaster---@ref{reread} can
be very useful when used in conjunction with @ref{if}.  See @ref{if} for details.)
The @ref{reread} command has no effect if input from standard input.

Examples:

Suppose the file "looper" contains the commands
@example
      a=a+1
      plot sin(x*a)
      pause -1
      if(a<5) reread
@end example

and from within `gnuplot` you submit the commands
@example
      a=0
      load 'looper'
@end example

The result will be five plots (separated by the @ref{pause} message).

Suppose the file "data" contains six columns of numbers with a total yrange
from 0 to 10; the first is x and the next are five different functions of x.
Suppose also that the file "plotter" contains the commands
@example
      c_p = c_p+1
      plot "$0" using 1:c_p with lines linetype c_p
      if(c_p <  n_p) reread
@end example

and from within `gnuplot` you submit the commands
@example
      n_p=6
      c_p=1
      unset key
      set yrange [0:10]
      set multiplot
      call 'plotter' 'data'
      unset multiplot
@end example

The result is a single graph consisting of five plots.  The yrange must be
set explicitly to guarantee that the five separate graphs (drawn on top of
each other in multiplot mode) will have exactly the same axes.  The linetype
must be specified; otherwise all the plots would be drawn with the same type.
See animate.dem in demo directory for an animated example.


@node reset, save, reread, Commands
@section reset

@c ?commands reset
@cindex reset
@cmindex reset


The @ref{reset} command causes all graph-related options that can be set with the
`set` command to take on their default values.  This command is useful, e.g.,
to restore the default graph settings at the end of a command file, or to
return to a defined state after lots of settings have been changed within a
command file.  Please refer to the `set` command to see the default values
that the various options take.

The following `set` commands do not change the graph status and are thus left
unchanged: the terminal set with `set term`, the output file set with @ref{output} and directory paths set with @ref{loadpath} and @ref{fontpath}.

@node save, set-show, reset, Commands
@section save

@c ^ <a name="save set"></a>
@c ?commands save
@cindex save
@cmindex save


The @ref{save} command saves user-defined functions, variables, the `set
term` status, all `set` options, or all of these, plus the last `plot`
(`splot`) command to the specified file.

Syntax:
@example
      save  @{<option>@} '<filename>'

@end example

where <option> is @ref{functions}, @ref{variables}, @ref{terminal} or `set`. If
no option is used, `gnuplot` saves functions, variables, `set`
options and the last `plot` (`splot`) command.

@ref{save}d files are written in text format and may be read by the
`load` command. For @ref{save} with the `set` option or without any
option, the @ref{terminal} choice and the @ref{output} filename are written
out as a comment, to get an output file that works in other
installations of gnuplot, without changes and without risk of
unwillingly overwriting files.

@ref{terminal} will write out just the @ref{terminal} status, without
the comment marker in front of it. This is mainly useful for
switching the @ref{terminal} setting for a short while, and getting back
to the previously set terminal, afterwards, by loading the saved
@ref{terminal} status. Note that for a single gnuplot session you may
rather use the other method of saving and restoring current terminal
by the commands `set term push` and `set term pop`, see `set term`.

The filename must be enclosed in quotes.

The special filename "-" may be used to @ref{save} commands to standard output.
On systems which support a popen function (Unix), the output of save can be
piped through an external program by starting the file name with a '|'.
This provides a consistent interface to `gnuplot`'s internal settings to
programs which communicate with `gnuplot` through a pipe.  Please see
help for `batch/interactive` for more details.

Examples:
@example
      save 'work.gnu'
      save functions 'func.dat'
      save var 'var.dat'
      save set 'options.dat'
      save term 'myterm.gnu'
      save '-'
      save '|grep title >t.gp'

@end example

@node set-show, shell, save, Commands
@section set-show

@c ?commands set
@c ?commands show
@cindex set

@cindex show

@c ?show all
The `set` command can be used to set _lots_ of options.  No screen is
drawn, however, until a `plot`, `splot`, or @ref{replot} command is given.

The `show` command shows their settings;  `show all` shows all the
settings.

Options changed using `set` can be returned to the default state by giving the
corresponding @ref{unset} command.  See also the @ref{reset} command, which returns
all settable parameters to default values.

If a variable contains time/date data, `show` will display it according to
the format currently defined by @ref{timefmt}, even if that was not in effect
when the variable was initially defined.

@menu
* angles::                      
* arrow::                       
* autoscale::                   
* bars::                        
* bmargin::                     
* border::                      
* boxwidth::                    
* clabel::                      
* clip::                        
* cntrparam::                   
* color_box::                   
* contour::                     
* data_style::                  
* datafile::                    
* decimalsign::                 
* dgrid3d::                     
* dummy::                       
* encoding::                    
* fit_::                        
* fontpath::                    
* format_::                     
* function_style::              
* functions::                   
* grid::                        
* hidden3d::                    
* historysize::                 
* isosamples::                  
* key::                         
* label::                       
* lmargin::                     
* loadpath::                    
* locale::                      
* logscale::                    
* macros::                      
* mapping::                     
* margin::                      
* mouse::                       
* multiplot::                   
* mx2tics::                     
* mxtics::                      
* my2tics::                     
* mytics::                      
* mztics::                      
* offsets::                     
* origin::                      
* output::                      
* parametric_::                 
* plot_::                       
* pm3d::                        
* palette::                     
* pointsize::                   
* polar::                       
* print_::                      
* object::                      
* rmargin::                     
* rrange::                      
* samples::                     
* size::                        
* style::                       
* surface::                     
* table::                       
* terminal::                    
* termoption::                  
* tics::                        
* ticslevel::                   
* ticscale::                    
* timestamp::                   
* timefmt::                     
* title_::                      
* tmargin::                     
* trange::                      
* urange::                      
* variables::                   
* version::                     
* view::                        
* vrange::                      
* x2data::                      
* x2dtics::                     
* x2label::                     
* x2mtics::                     
* x2range::                     
* x2tics::                      
* x2zeroaxis::                  
* xdata::                       
* xdtics::                      
* xlabel::                      
* xmtics::                      
* xrange::                      
* xtics::                       
* xyplane::                     
* xzeroaxis::                   
* y2data::                      
* y2dtics::                     
* y2label::                     
* y2mtics::                     
* y2range::                     
* y2tics::                      
* y2zeroaxis::                  
* ydata::                       
* ydtics::                      
* ylabel::                      
* ymtics::                      
* yrange::                      
* ytics::                       
* yzeroaxis::                   
* zdata::                       
* zdtics::                      
* zzeroaxis::                   
* cbdata::                      
* cbdtics::                     
* zero::                        
* zeroaxis::                    
* zlabel::                      
* zmtics::                      
* zrange::                      
* ztics::                       
* cblabel::                     
* cbmtics::                     
* cbrange::                     
* cbtics::                      
@end menu

@node angles, arrow, set-show, set-show
@subsection angles

@c ?commands set angles
@c ?commands show angles
@c ?set angles
@c ?show angles
@cindex angles
@opindex angles


@c ?commands set angles degrees
@c ?set angles degrees
@c ?angles degrees
@cindex degrees

By default, `gnuplot` assumes the independent variable in polar graphs is in
units of radians.  If `set angles degrees` is specified before `set polar`,
then the default range is [0:360] and the independent variable has units of
degrees.  This is particularly useful for plots of data files.  The angle
setting also applies to 3-d mapping as set via the @ref{mapping} command.

Syntax:
@example
      set angles @{degrees | radians@}
      show angles

@end example

The angle specified in `set grid polar` is also read and displayed in the
units specified by @ref{angles}.

@ref{angles} also affects the arguments of the machine-defined functions
sin(x), cos(x) and tan(x), and the outputs of asin(x), acos(x), atan(x),
atan2(x), and arg(x).  It has no effect on the arguments of hyperbolic
functions or Bessel functions.  However, the output arguments of inverse
hyperbolic functions of complex arguments are affected; if these functions
are used, `set angles radians` must be in effect to maintain consistency
between input and output arguments.

@example
      x=@{1.0,0.1@}
      set angles radians
      y=sinh(x)
      print y         #prints @{1.16933, 0.154051@}
      print asinh(y)  #prints @{1.0, 0.1@}
@end example

but
@example
      set angles degrees
      y=sinh(x)
      print y         #prints @{1.16933, 0.154051@}
      print asinh(y)  #prints @{57.29578, 5.729578@}
@end example

See also
@uref{http://www.gnuplot.info/demo/poldat.html,poldat.dem: polar plot using @ref{angles} demo.
}

@node arrow, autoscale, angles, set-show
@subsection arrow

@c ?commands set arrow
@c ?commands unset arrow
@c ?commands show arrow
@c ?set arrow
@c ?unset arrow
@c ?show arrow
@cindex arrow
@opindex arrow


@cindex noarrow

Arbitrary arrows can be placed on a plot using the @ref{arrow} command.

Syntax:
@example
      set arrow @{<tag>@} @{from <position>@} @{to|rto <position>@}
                @{ @{arrowstyle | as <arrow_style>@}
                  | @{ @{nohead | head | backhead | heads@}
                      @{size <length>,<angle>@{,<backangle>@}@}
                      @{filled | empty | nofilled@}
                      @{front | back@}
                      @{ @{linestyle | ls <line_style>@}
                        | @{linetype | lt <line_type>@}
                          @{linewidth | lw <line_width@} @} @} @}

@end example

@example
      unset arrow @{<tag>@}
      show arrow @{<tag>@}

@end example

<tag> is an integer that identifies the arrow.  If no tag is given, the
lowest unused tag value is assigned automatically.  The tag can be used to
delete or change a specific arrow.  To change any attribute of an existing
arrow, use the @ref{arrow} command with the appropriate tag and specify the
parts of the arrow to be changed.

The <position>s are specified by either x,y or x,y,z, and may be preceded by
`first`, `second`, `graph`, `screen`, or `character` to select the coordinate
system.  Unspecified coordinates default to 0.  The end points can be
specified in one of five coordinate systems---`first` or `second` axes,
`graph`, `screen`, or `character`.  See `coordinates` for details.  A
coordinate system specifier does not carry over from the "from" position to
the "to" position.  Arrows outside the screen boundaries are permitted but
may cause device errors.  If the end point is specified by "rto" instead of
"to" it is drawn relatively to the start point.  For linear axes, `graph`
and `screen` coordinates, the distance between the start and the end point
corresponds to the given relative coordinate.  For logarithmic axes, the
relative given coordinate corresponds to the factor of the coordinate
between start and end point.  Thus, a negative relative value or zero are
not allowed for logarithmic axes.

Specifying `nohead` produces an arrow drawn without a head---a line segment.
This gives you yet another way to draw a line segment on the plot.  By
default, an arrow has a head at its end. Specifying `backhead` draws an arrow
head at the start point of the arrow while `heads` draws arrow heads on both
ends of the line.  Not all terminal types support double-ended arrows.

Head size can be controlled by `size <length>,<angle>` or
`size <length>,<angle>,<backangle>`, where `<length>` defines length of each
branch of the arrow head and `<angle>` the angle (in degrees) they make with
the arrow.  `<Length>` is in x-axis units; this can be changed by `first`,
`second`, `graph`, `screen`, or `character` before the <length>;  see
`coordinates` for details.  `<Backangle>` only takes effect when `filled`
or `empty` is also used.  Then, `<backangle>` is the angle (in degrees) the
back branches make with the arrow (in the same direction as `<angle>`).
The `fig` terminal has a restricted backangle function. It supports three
different angles. There are two thresholds: Below 70 degrees, the arrow head
gets an indented back angle. Above 110 degrees, the arrow head has an acute
back angle. Between these thresholds, the back line is straight.

Specifying `filled` produces filled arrow heads (if heads are used).
Filling is supported on filled-polygon capable terminals, see help of @ref{pm3d}
for their list, otherwise the arrow heads are closed but not filled.
The same result (closed but not filled arrow head) is reached by specifying
`empty`.  Further, filling and outline is obviously not supported on
terminals drawing arrows by their own specific routines, like `metafont`,
`metapost`, `latex` or `tgif`.

The line style may be selected from a user-defined list of line styles
(see `set style line`) or may be defined here by providing values for
<line_type> (an index from the default list of styles) and/or <line_width>
(which is a  multiplier for the default width).

Note, however, that if a user-defined line style has been selected, its
properties (type and width) cannot be altered merely by issuing another
@ref{arrow} command with the appropriate index and `lt` or `lw`.

If `front` is given, the arrow is written on top of the graphed data. If
`back` is given (the default), the arrow is written underneath the graphed
data.  Using `front` will prevent an arrow from being obscured by dense data.

Examples:

To set an arrow pointing from the origin to (1,2) with user-defined style 5,
use:
@example
      set arrow to 1,2 ls 5

@end example

To set an arrow from bottom left of plotting area to (-5,5,3), and tag the
arrow number 3, use:
@example
      set arrow 3 from graph 0,0 to -5,5,3

@end example

To change the preceding arrow to end at 1,1,1, without an arrow head and
double its width, use:
@example
      set arrow 3 to 1,1,1 nohead lw 2

@end example

To draw a vertical line from the bottom to the top of the graph at x=3, use:
@example
      set arrow from 3, graph 0 to 3, graph 1 nohead

@end example

To draw a vertical arrow with T-shape ends, use:
@example
      set arrow 3 from 0,-5 to 0,5 heads size screen 0.1,90

@end example

To draw an arrow relatively to the start point, where the relative distances
are given in graph coordinates, use:
@example
      set arrow from 0,-5 rto graph 0.1,0.1

@end example

To draw an arrow with relative end point in logarithmic x axis, use:
@example
      set logscale x
      set arrow from 100,-5 rto 10,10
@end example

This draws an arrow from 100,-5 to 1000,5. For the logarithmic x axis, the
relative coordinate 10 means "factor 10" while for the linear y axis, the
relative coordinate 10 means "difference 10".

To delete arrow number 2, use:
@example
      unset arrow 2

@end example

To delete all arrows, use:
@example
      unset arrow

@end example

To show all arrows (in tag order), use:
@example
      show arrow

@end example

@uref{http://gnuplot.sourceforge.net/demo/arrowstyle.html,arrows demos.
}


@node autoscale, bars, arrow, set-show
@subsection autoscale

@c ?commands set autoscale
@c ?commands unset autoscale
@c ?commands show autoscale
@c ?set autoscale
@c ?unset autoscale
@c ?show autoscale
@cindex autoscale
@opindex autoscale


@cindex noautoscale

Autoscaling may be set individually on the x, y or z axis or globally on all
axes. The default is to autoscale all axes.

Syntax:
@example
      set autoscale @{<axes>@{|min|max|fixmin|fixmax|fix@} | fix | keepfix@}
      unset autoscale @{<axes>@}
      show autoscale

@end example

where <axes> is either `x`, `y`, `z`, `cb`, `x2`, `y2` or `xy`.  A keyword with
`min` or `max` appended (this cannot be done with `xy`) tells `gnuplot` to
autoscale just the minimum or maximum of that axis.  If no keyword is given,
all axes are autoscaled.

A keyword with `fixmin`, `fixmax` or `fix` appended tells gnuplot to disable
extension of the axis range to the next tic mark position, for autoscaled
axes using equidistant tics; `set autoscale fix` sets this for all axes.
Command `set autoscale keepfix` autoscales all axes while keeping the fix
settings.

When autoscaling, the axis range is automatically computed and the dependent
axis (y for a `plot` and z for `splot`) is scaled to include the range of the
function or data being plotted.

If autoscaling of the dependent axis (y or z) is not set, the current y or z
range is used.

Autoscaling the independent variables (x for `plot` and x,y for `splot`) is a
request to set the domain to match any data file being plotted.  If there are
no data files, autoscaling an independent variable has no effect.  In other
words, in the absence of a data file, functions alone do not affect the x
range (or the y range if plotting z = f(x,y)).

Please see @ref{xrange} for additional information about ranges.

The behavior of autoscaling remains consistent in parametric mode, (see
`set parametric`).  However, there are more dependent variables and hence more
control over x, y, and z axis scales.  In parametric mode, the independent or
dummy variable is t for `plot`s and u,v for `splot`s.  @ref{autoscale} in
parametric mode, then, controls all ranges (t, u, v, x, y, and z) and allows
x, y, and z to be fully autoscaled.

Autoscaling works the same way for polar mode as it does for parametric mode
for `plot`, with the extension that in polar mode @ref{dummy} can be used to
change the independent variable from t (see @ref{dummy}).

When tics are displayed on second axes but no plot has been specified for
those axes, x2range and y2range are inherited from xrange and yrange.  This
is done _before_ xrange and yrange are autoextended to a whole number of
tics, which can cause unexpected results.  You can use the `fixmin`
or `fixmax` options to avoid this.

Examples:

This sets autoscaling of the y axis (other axes are not affected):
@example
      set autoscale y

@end example

This sets autoscaling only for the minimum of the y axis (the maximum of the
y axis and the other axes are not affected):
@example
      set autoscale ymin

@end example

This disables extension of the x2 axis tics to the next tic mark,
thus keeping the exact range as found in the plotted data and functions:
@example
      set autoscale x2fixmin
      set autoscale x2fixmax

@end example

This sets autoscaling of the x and y axes:
@example
      set autoscale xy

@end example

This sets autoscaling of the x, y, z, x2 and y2 axes:
@example
      set autoscale

@end example

This disables autoscaling of the x, y, z, x2 and y2 axes:
@example
      unset autoscale

@end example

This disables autoscaling of the z axis only:
@example
      unset autoscale z

@end example

@menu
* parametric_mode::             
* polar_mode::                  
@end menu

@node parametric_mode, polar_mode, autoscale, autoscale
@subsubsection parametric mode

@c ?commands set autoscale parametric
@c ?set autoscale parametric
@c ?set autoscale t
When in parametric mode (`set parametric`), the xrange is as fully scalable
as the y range.  In other words, in parametric mode the x axis can be
automatically scaled to fit the range of the parametric function that is
being plotted.  Of course, the y axis can also be automatically scaled just
as in the non-parametric case.  If autoscaling on the x axis is not set, the
current x range is used.

Data files are plotted the same in parametric and non-parametric mode.
However, there is a difference in mixed function and data plots: in
non-parametric mode with autoscaled x, the x range of the datafile controls
the x range of the functions; in parametric mode it has no influence.

For completeness a last command `set autoscale t` is accepted.  However, the
effect of this "scaling" is very minor.  When `gnuplot` determines that the
t range would be empty, it makes a small adjustment if autoscaling is true.
Otherwise, `gnuplot` gives an error.  Such behavior may, in fact, not be very
useful and the command `set autoscale t` is certainly questionable.

`splot` extends the above ideas as you would expect.  If autoscaling is set,
then x, y, and z ranges are computed and each axis scaled to fit the
resulting data.

@node polar_mode,  , parametric_mode, autoscale
@subsubsection polar mode

@c ?commands set autoscale polar
@c ?set autoscale polar
When in polar mode (`set polar`), the xrange and the yrange are both found
from the polar coordinates, and thus they can both be automatically scaled.
In other words, in polar mode both the x and y axes can be automatically
scaled to fit the ranges of the polar function that is being plotted.

When plotting functions in polar mode, the rrange may be autoscaled.  When
plotting data files in polar mode, the trange may also be autoscaled.  Note
that if the trange is contained within one quadrant, autoscaling will produce
a polar plot of only that single quadrant.

Explicitly setting one or two ranges but not others may lead to unexpected
results.
See also
@uref{http://www.gnuplot.info/demo/poldat.html,polar demos.
}

@node bars, bmargin, autoscale, set-show
@subsection bars

@c ?commands set bars
@c ?commands show bars
@c ?set bars
@c ?show bars
@cindex bars
@opindex bars


The @ref{bars} command controls the tics at the ends of error bars,
and also the width of the boxes in plot styles candlesticks and
financebars.

Syntax:
@example
      set bars @{small | large | fullwidth | <size>@}
      unset bars
      show bars

@end example

`small` is a synonym for 0.0, and `large` for 1.0.
The default is 1.0 if no size is given.

The keyword `fullwidth` is relevant only to histograms with errorbars.
It sets the width of the errorbar ends to be the same as the width of the
associated box in the histogram.  It does not change the width of the box
itself.

@node bmargin, border, bars, set-show
@subsection bmargin

@c ?commands set bmargin
@c ?set bmargin
@cindex bmargin
@opindex bmargin


The command @ref{bmargin} sets the size of the bottom margin.
Please see @ref{margin} for details.

@node border, boxwidth, bmargin, set-show
@subsection border

@c ?commands set border
@c ?commands unset border
@c ?commands show border
@c ?set border
@c ?unset border
@c ?show border
@cindex border
@opindex border


@cindex noborder

The @ref{border} and @ref{border} commands control the display of the graph
borders for the `plot` and `splot` commands.  Note that the borders do not
necessarily coincide with the axes; with `plot` they often do, but with
`splot` they usually do not.

Syntax:
@example
      set border @{<integer>@} @{front | back@} @{linewidth | lw <line_width>@}
                 @{@{linestyle | ls <line_style>@} | @{linetype | lt <line_type>@}@}
      unset border
      show border

@end example

With a `splot` displayed in an arbitrary orientation, like `set view 56,103`,
the four corners of the x-y plane can be referred to as "front", "back",
"left" and "right".  A similar set of four corners exist for the top surface,
of course.  Thus the border connecting, say, the back and right corners of the
x-y plane is the "bottom right back" border, and the border connecting the top
and bottom front corners is the "front vertical".  (This nomenclature is
defined solely to allow the reader to figure out the table that follows.)

The borders are encoded in a 12-bit integer: the bottom four bits control the
border for `plot` and the sides of the base for `splot`; the next four bits
control the verticals in `splot`; the top four bits control the edges on top
of the `splot`.  In detail, `<integer>` should be the sum of the appropriate
entries from the following table:


@example
            Bit     plot        splot
              1   bottom      bottom left front
              2   left        bottom left back
              4   top         bottom right front
              8   right       bottom right back
             16   no effect   left vertical
             32   no effect   back vertical
             64   no effect   right vertical
            128   no effect   front vertical
            256   no effect   top left back
            512   no effect   top right back
           1024   no effect   top left front
           2048   no effect   top right front

@end example


Various bits or combinations of bits may be added together in the command.

The default is 31, which is all four sides for `plot`, and base and z axis
for `splot`.

In 2D plots the border is normally drawn on top of all plots elements
(`front`). If you want the border to be drawn behind the plot elements,
use `set border back`.

Using the optional <line_style>, <line_type> and <line_width> specifiers, the
way the border lines are drawn can be influenced (limited by what the current
terminal driver supports).

For `plot`, tics may be drawn on edges other than bottom and left by enabling
the second axes -- see `set xtics` for details.

If a `splot` draws only on the base, as is the case with "`unset surface; set
contour base`", then the verticals and the top are not drawn even if they are
specified.

The `set grid` options 'back', 'front' and 'layerdefault' also
control the order in which the border lines are drawn with respect to
the output of the plotted data.

Examples:

Draw default borders:
@example
      set border

@end example

Draw only the left and bottom (`plot`) or both front and back bottom left
(`splot`) borders:
@example
      set border 3

@end example

Draw a complete box around a `splot`:
@example
      set border 4095

@end example

Draw a topless box around a `splot`, omitting the front vertical:
@example
      set border 127+256+512 # or set border 1023-128

@end example

Draw only the top and right borders for a `plot` and label them as axes:
@example
      unset xtics; unset ytics; set x2tics; set y2tics; set border 12

@end example


@node boxwidth, clabel, border, set-show
@subsection boxwidth

@c ?commands set boxwidth
@c ?commands show boxwidth
@c ?set boxwidth
@c ?show boxwidth
@cindex boxwidth
@opindex boxwidth


The @ref{boxwidth} command is used to set the default width of boxes in the
`boxes`, `boxerrorbars`, `candlesticks` and `histograms` styles.

Syntax:
@example
      set boxwidth @{<width>@} @{absolute|relative@}
      show boxwidth

@end example

By default, adjacent boxes are extended in width until they touch each other.
A different default width may be specified using the @ref{boxwidth} command.
`Relative` widths are interpreted as being a fraction of this default width.

An explicit value for the boxwidth is interpreted as being a number of units
along the current x axis (`absolute`) unless the modifier `relative` is given.
If the x axis is a log-scale (see `set log`) then the value of boxwidth is
truly "absolute" only at x=1; this physical width is maintained everywhere
along the axis (i.e. the boxes do not become narrower the value of x
increases). If the range spanned by a log scale x axis is far from x=1,
some experimentation may be required to find a useful value of boxwidth.

The default is superseded by explicit width information taken from an extra
data column in styles `boxes` or `boxerrorbars`.  In a four-column data set,
the fourth column will be interpreted as the box width unless the width is set
to -2.0, in which case the width will be calculated automatically.
See `style boxes` and `style boxerrorbars` for more details.

To set the box width to automatic use the command
@example
      set boxwidth

@end example

or, for four-column data,
@example
      set boxwidth -2

@end example

The same effect can be achieved with the @ref{using} keyword in `plot`:
@example
      plot 'file' using 1:2:3:4:(-2)

@end example

To set the box width to half of the automatic size use
@example
      set boxwidth 0.5 relative

@end example

To set the box width to an absolute value of 2 use
@example
      set boxwidth 2 absolute

@end example

@node clabel, clip, boxwidth, set-show
@subsection clabel

@c ?commands set clabel
@c ?commands unset clabel
@c ?commands show clabel
@c ?set clabel
@c ?unset clabel
@c ?show clabel
@cindex clabel
@opindex clabel


`gnuplot` will vary the linetype used for each contour level when clabel is
set.  When this option on (the default), a legend labels each linestyle with
the z level it represents.  It is not possible at present to separate the
contour labels from the surface key.

Syntax:
@example
      set clabel @{'<format>'@}
      unset clabel
      show clabel

@end example

The default for the format string is %8.3g, which gives three decimal places.
This may produce poor label alignment if the key is altered from its default
configuration.

The first contour linetype, or only contour linetype when clabel is off, is
the surface linetype +1; contour points are the same style as surface points.

See also @ref{contour}.

@node clip, cntrparam, clabel, set-show
@subsection clip

@c ?commands set clip
@c ?commands unset clip
@c ?commands show clip
@c ?set clip
@c ?unset clip
@c ?show clip
@cindex clip
@opindex clip


@cindex noclip

`gnuplot` can clip data points and lines that are near the boundaries of a
graph.

Syntax:
@example
      set clip <clip-type>
      unset clip <clip-type>
      show clip

@end example

Three clip types for points and lines are supported by `gnuplot`: `points`,
`one`, and `two`. One, two, or all three clip types may be active for a
single graph.
Note that clipping of color filled quadrangles drawn by @ref{pm3d} maps and
surfaces is not controlled by this command, but by `set pm3d clip1in` and
`set pm3d clip4in`.

The `points` clip type forces `gnuplot` to clip (actually, not plot at all)
data points that fall within but too close to the boundaries.  This is done
so that large symbols used for points will not extend outside the boundary
lines.  Without clipping points near the boundaries, the plot may look bad.
Adjusting the x and y ranges may give similar results.

Setting the `one` clip type causes `gnuplot` to draw a line segment which has
only one of its two endpoints within the graph.  Only the in-range portion of
the line is drawn.  The alternative is to not draw any portion of the line
segment.

Some lines may have both endpoints out of range, but pass through the graph.
Setting the `two` clip-type allows the visible portion of these lines to be
drawn.

In no case is a line drawn outside the graph.

The defaults are `noclip points`, `clip one`, and `noclip two`.

To check the state of all forms of clipping, use
@example
      show clip

@end example

For backward compatibility with older versions, the following forms are also
permitted:
@example
      set clip
      unset clip

@end example

@ref{clip} is synonymous with `set clip points`; @ref{clip} turns off all
three types of clipping.

@node cntrparam, color_box, clip, set-show
@subsection cntrparam

@c ?commands set cntrparam
@c ?commands show cntrparam
@c ?set cntrparam
@c ?show cntrparam
@cindex cntrparam
@opindex cntrparam


@ref{cntrparam} controls the generation of contours and their smoothness for
a contour plot. @ref{contour} displays current settings of @ref{cntrparam} as
well as @ref{contour}.

Syntax:
@example
      set cntrparam @{ @{ linear
                      | cubicspline
                      | bspline
                      | points <n>
                      | order <n>
                      | levels @{ auto @{<n>@} | <n>
                                 | discrete <z1> @{,<z2>@{,<z3>...@}@}
                                 | incremental <start>, <incr> @{,<end>@}
                               @}
                      @}
                    @}
      show contour

@end example

This command has two functions.  First, it sets the values of z for which
contour points are to be determined (by linear interpolation between data
points or function isosamples.)  Second, it controls the way contours are
drawn between the points determined to be of equal z.  <n> should be an
integral constant expression and <z1>, <z2> ... any constant expressions.
The parameters are:

`linear`, `cubicspline`, `bspline`---Controls type of approximation or
interpolation.  If `linear`, then straight line segments connect points of
equal z magnitude.  If `cubicspline`, then piecewise-linear contours are
interpolated between the same equal z points to form somewhat smoother
contours, but which may undulate.  If `bspline`, a guaranteed-smoother curve
is drawn, which only approximates the position of the points of equal-z.

`points`---Eventually all drawings are done with piecewise-linear strokes.
This number controls the number of line segments used to approximate the
`bspline` or `cubicspline` curve.  Number of cubicspline or bspline
segments (strokes) = `points` * number of linear segments.

`order`---Order of the bspline approximation to be used.  The bigger this
order is, the smoother the resulting contour.  (Of course, higher order
bspline curves will move further away from the original piecewise linear
data.)  This option is relevant for `bspline` mode only.  Allowed values are
integers in the range from 2 (linear) to 10.

`levels`--- Selection of contour levels,  controlled by `auto` (default),
`discrete`, `incremental`, and <n>, number of contour levels.

For `auto`, <n> specifies a nominal number of levels; the actual number will
be adjusted to give simple labels. If the surface is bounded by zmin and zmax,
contours will be generated at integer multiples of dz between zmin and zmax,
where dz is 1, 2, or 5 times some power of ten (like the step between two
tic marks).

For `levels discrete`, contours will be generated at z = <z1>, <z2> ... as
specified; the number of discrete levels sets the number of contour levels.
In `discrete` mode, any `set cntrparam levels <n>` are ignored.

For `incremental`, contours are generated at values of z beginning at <start>
and increasing by <increment>, until the number of contours is reached. <end>
is used to determine the number of contour levels, which will be changed by
any subsequent `set cntrparam levels <n>`.  If the z axis is logarithmic,
<increment> will be interpreted as a factor, just like in @ref{ztics}.

If the command @ref{cntrparam} is given without any arguments specified,  the
defaults are used: linear, 5 points, order 4, 5 auto levels.

Examples:
@example
      set cntrparam bspline
      set cntrparam points 7
      set cntrparam order 10

@end example

To select levels automatically, 5 if the level increment criteria are met:
@example
      set cntrparam levels auto 5

@end example

To specify discrete levels at .1, .37, and .9:
@example
      set cntrparam levels discrete .1,1/exp(1),.9

@end example

To specify levels from 0 to 4 with increment 1:
@example
      set cntrparam levels incremental  0,1,4

@end example

To set the number of levels to 10 (changing an incremental end or possibly
the number of auto levels):
@example
      set cntrparam levels 10

@end example

To set the start and increment while retaining the number of levels:
@example
      set cntrparam levels incremental 100,50

@end example

See also @ref{contour} for control of where the contours are drawn, and
@ref{clabel} for control of the format of the contour labels and linetypes.

See also
@uref{http://www.gnuplot.info/demo/contours.html,contours demo (contours.dem)
}
and
@uref{http://www.gnuplot.info/demo/discrete.html,contours with user defined levels demo (discrete.dem).
}

@node color_box, contour, cntrparam, set-show
@subsection color box

@c ?commands set colorbox
@c ?commands show colorbox
@c ?commands unset colorbox
@c ?set colorbox
@c ?show colorbox
@c ?unset colorbox
@cindex colorbox


The color scheme, i.e. the gradient of the smooth color with min_z and
max_z values of @ref{pm3d}'s @ref{palette}, is drawn in a color box unless `unset
colorbox`.

@example
      set colorbox
      set colorbox @{
                 @{ vertical | horizontal @}
                 @{ default | user @}
                 @{ origin x, y @}
                 @{ size x, y @}
                 @{ front | back @}
                 @{ noborder | bdefault | border [line style] @}
               @}
      show colorbox
      unset colorbox

@end example

Color box position can be `default` or `user`.  If the latter is specified the
values as given with the @ref{origin} and @ref{size} subcommands are used. The box
can be drawn after (`front`) or before (`back`) the graph or the surface.

The orientation of the color gradient can be switched by options `vertical`
and `horizontal`.

`origin x, y` and `size x, y` are used only in combination with the `user`
option. The x and y values are interpreted as screen coordinates by default,
and this is the only legal option for 3D plots. 2D plots, including splot with
`set view map`, allow any coordinate system to be specified.  Try for example:
@example
    set colorbox horiz user origin .1,.02 size .8,.04
@end example

which will draw a horizontal gradient somewhere at the bottom of the graph.

@ref{border} turns the border on (this is the default). `noborder` turns the border
off. If an positive integer argument is given after @ref{border}, it is used as a
line style tag which is used for drawing the border, e.g.:
@example
    set style line 2604 linetype -1 linewidth .4
    set colorbox border 2604
@end example

will use line style `2604`, a thin line with the default border color (-1)
for drawing the border. `bdefault` (which is the default) will use the default
border line style for drawing the border of the color box.

The axis of the color box is called `cb` and it is controlled by means of the
usual axes commands, i.e. `set/unset/show` with @ref{cbrange}, `[m]cbtics`,
`format cb`, `grid [m]cb`, @ref{cblabel}, and perhaps even @ref{cbdata}, `[no]cbdtics`,
`[no]cbmtics`.

`set colorbox` without any parameter switches the position to default.
`unset colorbox` resets the default parameters for the colorbox and switches
the colorbox off.

See also help for @ref{pm3d}, @ref{palette}, @ref{pm3d}, and `set style line`.


@node contour, data_style, color_box, set-show
@subsection contour

@c ?commands set contour
@c ?commands unset contour
@c ?commands show contour
@c ?set contour
@c ?unset contour
@c ?show contour
@cindex contour
@opindex contour


@cindex nocontour

@ref{contour} enables contour drawing for surfaces.  This option is available
for `splot` only.  It requires grid data, see `grid_data` for more details.
If contours are desired from non-grid data, @ref{dgrid3d} can be used to
create an appropriate grid.

Syntax:
@example
      set contour @{base | surface | both@}
      unset contour
      show contour

@end example

The three options specify where to draw the contours: `base` draws the
contours on the grid base where the x/ytics are placed, @ref{surface} draws the
contours on the surfaces themselves, and `both` draws the contours on both
the base and the surface.  If no option is provided, the default is `base`.

See also @ref{cntrparam} for the parameters that affect the drawing of
contours, and @ref{clabel} for control of labelling of the contours.

The surface can be switched off (see @ref{surface}), giving a contour-only
graph.  Though it is possible to use @ref{size} to enlarge the plot to fill
the screen, more control over the output format can be obtained by writing
the contour information to a file, and rereading it as a 2-d datafile plot:

@example
      unset surface
      set contour
      set cntrparam ...
      set table 'filename'
      splot ...
      unset table
      # contour info now in filename
      set term <whatever>
      plot 'filename'

@end example

In order to draw contours, the data should be organized as "grid data".  In
such a file all the points for a single y-isoline are listed, then all the
points for the next y-isoline, and so on.  A single blank line (a line
containing no characters other than blank spaces and a carriage return and/or
a line feed) separates one y-isoline from the next.
See also @ref{datafile}.

See also
@uref{http://www.gnuplot.info/demo/contours.html,contours demo (contours.dem)
}
and
@uref{http://www.gnuplot.info/demo/discrete.html,contours with user defined levels demo (discrete.dem).
}

@node data_style, datafile, contour, set-show
@subsection data style

@c ?DUMMYLABEL set style data
This form of the command is deprecated. Please see `set style data`.

@node datafile, decimalsign, data_style, set-show
@subsection datafile

@c ?set datafile
@c ?show datafile
The @ref{datafile} command options control interpretation of fields read from
input data files by the `plot`, `splot`, and @ref{fit} commands.  Four such
options are currently implemented.

@menu
* set_datafile_fortran::        
* set_datafile_missing::        
* set_datafile_separator::      
* set_datafile_commentschars::  
* set_datafile_binary::         
@end menu

@node set_datafile_fortran, set_datafile_missing, datafile, datafile
@subsubsection set datafile fortran

@c ?set datafile fortran
@cindex fortran

The `set datafile fortran` command enables a special check for values in the
input file expressed as Fortran D or Q constants. This extra check slows down
the input process, and should only be selected if you do in fact have datafiles
containing Fortran D or Q constants. The option can be disabled again using
`unset datafile fortran`.

@node set_datafile_missing, set_datafile_separator, set_datafile_fortran, datafile
@subsubsection set datafile missing

@c ?set datafile missing
@c ?set missing
@cindex missing

The `set datafile missing` command allows you to tell `gnuplot` what character
string is used in a data file to denote missing data.  Exactly how this missing
value will be treated depends on the @ref{using} specifier of the `plot` or `splot`
command.

Syntax:
@example
      set datafile missing @{"<string>"@}
      show datafile missing
      unset datafile

@end example

Example:
@example
      # Ignore entries containing IEEE NaN ("Not a Number") code
      set datafile missing "NaN"

@end example

Example:
@example
      set datafile missing "?"
      set style data lines
      plot '-'
         1 10
         2 20
         3 ?
         4 40
         5 50
         e
      plot '-' using 1:2
         1 10
         2 20
         3 ?
         4 40
         5 50
         e
      plot '-' using 1:($2)
         1 10
         2 20
         3 ?
         4 40
         5 50
         e

@end example

The first `plot` will recognize only the first datum in the "3 ?" line.  It
will use the single-datum-on-a-line convention that the line number is "x"
and the datum is "y", so the point will be plotted (in this case erroneously)
at (2,3).

The second `plot` will correctly ignore the middle line.  The plotted line
will connect the points at (2,20) and (4,40).

The third `plot` will also correctly ignore the middle line, but the plotted
line will not connect the points at (2,20) and (4,40).

There is no default character for `missing`, but in many cases any
non-parsible string of characters found where a numerical value is expected
will be treated as missing data.


@node set_datafile_separator, set_datafile_commentschars, set_datafile_missing, datafile
@subsubsection set datafile separator

@c ?set datafile separator
@c ?show datafile separator
@c ?datafile separator
@cindex separator

The command `set datafile separator "<char>"` tells `gnuplot` that data fields
in subsequent input files are separated by <char> rather than by whitespace.
The most common use is to read in csv (comma-separated value) files written
by spreadsheet or database programs. By default data fields are separated by
whitespace.

Syntax:
@example
      set datafile separator @{"<char>" | whitespace@}

@end example

Examples:
@example
      # Input file contains tab-separated fields
      set datafile separator "\t"

@end example

@example
      # Input file contains comma-separated values fields
      set datafile separator ","

@end example

@node set_datafile_commentschars, set_datafile_binary, set_datafile_separator, datafile
@subsubsection set datafile commentschars

@c ?set datafile commentschars
@cindex commentschars

The `set datafile commentschars` command allows you to tell `gnuplot` what
characters are used in a data file to denote comments.  Gnuplot will ignore
rest of the line behind the specified characters if either of them is the
first non-blank character on the line.

Syntax:
@example
      set datafile commentschars @{"<string>"@}
      show datafile commentschars
      unset commentschars

@end example

Default value of the string is "#!" on VMS and "#" otherwise.

Then, the following line in a data file is completely ignored
@example
    # 1 2 3 4
@end example

but the following
@example
    1 # 3 4
@end example

produces rather unexpected plot unless
@example
    set datafile missing '#'
@end example

is specified as well.

Example:
@example
      set datafile commentschars "#!%"

@end example

@node set_datafile_binary,  , set_datafile_commentschars, datafile
@subsubsection set datafile binary

@c ?set datafile binary
The `set datafile binary` command is used to set the defaults when reading
binary data files.  The syntax matches precisely that used for commands
`plot` and `splot`.  See `binary` for details about <binary list>.

Syntax:
@example
      set datafile binary <binary list>
      show datafile binary
      show datafile
      unset datafile

@end example

Examples:
@example
      set datafile binary filetype=auto
      set datafile binary array=512x512 format="%uchar"

@end example

@node decimalsign, dgrid3d, datafile, set-show
@subsection decimalsign

@c ?commands set decimalsign
@c ?commands show decimalsign
@c ?commands unset decimalsign
@c ?set decimalsign
@c ?show decimalsign
@c ?unset decimalsign
@cindex decimalsign
@opindex decimalsign


@cindex locale
@opindex locale


The @ref{decimalsign} command selects a decimal sign for numbers printed
into tic labels or @ref{label} strings.

Syntax:
@example
      set decimalsign @{<value> | locale @{"<locale>"@}@}
      unset decimalsign
      show decimalsign

@end example

The argument <value> is a string to be used in place of the usual
decimal point. Typical choices include the period, '.', and the comma,
',', but others may be useful, too.  If you omit the <value> argument,
the decimal separator is not modified from the usual default, which is
a period.  Unsetting decimalsign has the same effect as omitting <value>.

Example:

Correct typesetting in most European countries requires:
@example
      set decimalsign ','

@end example

Please note: If you set an explicit string, this affects only numbers that
are printed using gnuplot's gprintf() formatting routine, include axis tics.
It does not affect the format expected for input data, and it does not affect
numbers printed with the sprintf() formatting routine. To change the behavior
of both input and output formatting, instead use the form

@example
      set decimalsign locale

@end example

This instructs the program to use both input and output formats in accordance
with the current setting of the LC_ALL, LC_NUMERIC, or LANG environmental
variables.

@example
      set decimalsign locale "foo"

@end example

This instructs the program to format all input and output in accordance with
locale "foo", which must be installed.  If locale "foo" is not found then an
error message is printed and the decimal sign setting is unchanged.
On linux systems you can get a list of the locales installed on your machine by
typing "locale -a". A typical linux locale string is of the form "sl_SI.UTF-8".
A typical Windows locale string is of the form "Slovenian_Slovenia.1250" or
"slovenian". Please note that interpretation of the locale settings is done by
the C library at runtime. Older C libraries may offer only partial support for
locale settings such as the thousands grouping separator character.

@example
      set decimalsign locale; set decimalsign "."

@end example

This sets all input and output to use whatever decimal sign is correct for
the current locale, but over-rides this with an explicit '.' in numbers
formatted using gnuplot's internal gprintf() function.

@node dgrid3d, dummy, decimalsign, set-show
@subsection dgrid3d

@c ?commands set dgrid3d
@c ?commands unset dgrid3d
@c ?commands show dgrid3d
@c ?set dgrid3d
@c ?unset dgrid3d
@c ?show dgrid3d
@cindex dgrid3d
@opindex dgrid3d


@cindex nodgrid3d

The @ref{dgrid3d} command enables, and can set parameters for, non-grid to
grid data mapping.  See `splot grid_data` for more details about the grid data
structure.

Syntax:
@example
      set dgrid3d @{<row_size>@} @{,@{<col_size>@} @{,<norm>@}@}
      unset dgrid3d
      show dgrid3d

@end example

By default @ref{dgrid3d} is disabled.  When enabled, 3-d data read from a file
are always treated as a scattered data set.  A grid with dimensions derived
from a bounding box of the scattered data and size as specified by the
row/col_size parameters is created for plotting and contouring.  The grid
is equally spaced in x (rows) and in y (columns); the z values are computed
as weighted averages of the scattered points' z values.

The third parameter, norm, controls the weighting:  Each data point is
weighted inversely by its distance from the grid point raised to the norm
power.  (Actually, the weights are given by the inverse of dx^norm + dy^norm,
where dx and dy are the components of the separation of the grid point from
each data point.  For some norms that are powers of two, specifically 4, 8,
and 16, the computation is optimized by using the Euclidean distance in the
weight calculation, (dx^2+dy^2)^norm/2.  However, any non-negative integer
can be used.)

The closer the data point is to a grid point, the more effect it has on
that grid point and the larger the value of norm the less effect more
distant data points have on that grid point.

The @ref{dgrid3d} option is a simple low pass filter that converts scattered
data to a grid data set.  More sophisticated approaches to this problem
exist and should be used to preprocess the data outside `gnuplot` if this
simple solution is found inadequate.

(The z values are found by weighting all data points, not by interpolating
between nearby data points;  also edge effects may produce unexpected and/or
undesired results.  In some cases, small norm values produce a grid point
reflecting the average of distant data points rather than a local average,
while large values of norm may produce "steps" with several grid points
having the same value as the closest data point, rather than making a smooth
transition between adjacent data points.  Some areas of a grid may be filled
by extrapolation, to an arbitrary boundary condition.  The variables are
not normalized; consequently the units used for x and y will affect the
relative weights of points in the x and y directions.)

Examples:
@example
      set dgrid3d 10,10,1     # defaults
      set dgrid3d ,,4

@end example

The first specifies that a grid of size 10 by 10 is to be constructed using
a norm value of 1 in the weight computation.  The second only modifies the
norm, changing it to 4.
See also
@uref{http://www.gnuplot.info/demo/scatter.html,scatter.dem: dgrid3d demo.
}


@node dummy, encoding, dgrid3d, set-show
@subsection dummy

@c ?commands set dummy
@c ?commands show dummy
@c ?set dummy
@c ?show dummy
@cindex dummy
@opindex dummy


The @ref{dummy} command changes the default dummy variable names.

Syntax:
@example
      set dummy @{<dummy-var>@} @{,<dummy-var>@}
      show dummy

@end example

By default, `gnuplot` assumes that the independent, or "dummy", variable for
the `plot` command is "t" if in parametric or polar mode, or "x" otherwise.
Similarly the independent variables for the `splot` command are "u" and "v"
in parametric mode (`splot` cannot be used in polar mode), or "x" and "y"
otherwise.

It may be more convenient to call a dummy variable by a more physically
meaningful or conventional name.  For example, when plotting time functions:

@example
      set dummy t
      plot sin(t), cos(t)

@end example

At least one dummy variable must be set on the command; @ref{dummy} by itself
will generate an error message.

Examples:
@example
      set dummy u,v
      set dummy ,s

@end example

The second example sets the second variable to s.

@node encoding, fit_, dummy, set-show
@subsection encoding

@c ?commands set encoding
@c ?commands show encoding
@c ?set encoding
@c ?show encoding
@cindex encoding
@opindex encoding


@cindex encodings

The @ref{encoding} command selects a character encoding.
Syntax:
@example
      set encoding @{<value>@}
      show encoding

@end example

Valid values are
@example
   default     - tells a terminal to use its default encoding
   iso_8859_1  - the most common Western European font used by many
                 Unix workstations and by MS-Windows. This encoding is
                 known in the PostScript world as 'ISO-Latin1'.
   iso_8859_2  - used in Central and Eastern Europe
   iso_8859_15 - a variant of iso_8859_1 that includes the Euro symbol
   koi8r       - popular Unix cyrillic encoding
   koi8u       - ukrainian Unix cyrillic encoding
   cp437       - codepage for MS-DOS
   cp850       - codepage for OS/2, Western Europe
   cp852       - codepage for OS/2, Central and Eastern Europe
   cp1250      - codepage for MS Windows, Central and Eastern Europe

@end example

Generally you must set the encoding before setting the terminal type.
Note that encoding is not supported by all terminal drivers and that
the device must be able to produce the desired non-standard characters.
The PostScript, X11 and wxt terminals support all encodings. OS/2 Presentation
Manager switches automatically to codepage 912 for `iso_8859_2`.

@node fit_, fontpath, encoding, set-show
@subsection fit

@c ?commands set fit
@c ?commands show fit
@c ?set fit
@c ?show fit
The @ref{fit} setting defines where the @ref{fit} command writes its output.
If this option was built into your version of gnuplot, it also controls
whether parameter errors from the fit will be written into variables.

Syntax:
@example
      set fit @{logfile @{"<filename>"@}@} @{@{no@}errorvariables@}
      unset fit
      show fit

@end example

The <filename> argument must be enclosed in single or double quotes.

If no filename is given or @ref{fit} is used the log file is
reset to its default value "fit.log" or the value of the environmental
variable `FIT_LOG`.

Users of DOS-like platforms should note that the \ character has
special significance in double-quoted strings, so single-quotes
should be used for filenames in different directories, or you have
to write \\ for each \.  Or you can just use forward slashes,
even though this is DOS.

If the given logfile name ends with a / or \, it is interpreted to be
a directory name, and the actual filename will be "fit.log" in that
directory.

If the `errorvariables` option is turned on, the error of each fitted
parameter computed by @ref{fit} will be copied to a user-defined variable
whose name is formed by appending "_err" to the name of the parameter
itself.  This is useful mainly to put the parameter and its error onto
a plot of the data and the fitted function, for reference, as in:

@example
       set fit errorvariables
       fit f(x) 'datafile' using 1:2 via a, b
       print "error of a is:", a_err
       set label 'a=%6.2f', a, '+/- %6.2f', a_err
       plot 'datafile' using 1:2, f(x)

@end example

@node fontpath, format_, fit_, set-show
@subsection fontpath

@c ?commands set fontpath
@c ?commands show fontpath
@c ?set fontpath
@c ?show fontpath
@cindex fontpath
@opindex fontpath


The @ref{fontpath} setting defines additional locations for font files
searched when including font files. Currently only the postscript terminal
supports @ref{fontpath}. If a file cannot be found in the current directory,
the directories in @ref{fontpath} are tried. Further documentation concerning
the supported file formats is included in the @ref{postscript} section
of the documentation.

Syntax:
@example
      set fontpath @{"pathlist1" @{"pathlist2"...@}@}
      show fontpath

@end example

Path names may be entered as single directory names, or as a list of
path names separated by a platform-specific path separator, eg. colon
(':') on Unix, semicolon (';') on DOS/Windows/OS/2/Amiga platforms.
The @ref{fontpath}, @ref{save} and `save set` commands replace the
platform-specific separator with a space character (' ') for maximum
portability. If a directory name ends with an exclamation mark ('!') also
the subdirectories of this directory are searched for font files.

If the environmental variable GNUPLOT_FONTPATH is set, its contents are
appended to @ref{fontpath}.  If it is not set, a system dependent default value
is used. It is set by testing several directories for existence when using
the fontpath the first time. Thus, the first call of @ref{fontpath},
@ref{fontpath}, @ref{fontpath}, `plot`, or `splot` with embedded font
files takes a little more time. If you want to save this time you may
set the environmental variable GNUPLOT_FONTPATH since probing is switched
off, then. You can find out which is the default fontpath by using
@ref{fontpath}.

However, @ref{fontpath} prints the contents of user defined fontpath and
system fontpath separately.  Also, the @ref{save} and `save set` commands save
only the user specified parts of @ref{fontpath}, for portability reasons.

Many other terminal drivers access TrueType fonts via the gd library.
For these drivers the font search path is controlled by the environmental
variable GDFONTPATH.

@node format_, function_style, fontpath, set-show
@subsection format

@c ?commands set format
@c ?commands show format
@c ?set format
@c ?show format
@cindex format
@opindex format


@c ?format cb
The format of the tic-mark labels can be set with the `set format` command
or with the `set tics format` or individual `set @{axis@}tics format` commands.

Syntax:
@example
      set format @{<axes>@} @{"<format-string>"@}
      set format @{<axes>@} @{'<format-string>'@}
      show format

@end example

where <axes> is either `x`, `y`, `xy`, `x2`, `y2`, `z`, `cb` or
nothing (which refers to all axes at once).  The length of the string
representing a tic mark (after formatting with 'printf') is restricted
to 100 characters.  If the format string is omitted, the format will
be returned to the default "% g".  For LaTeX users, the format "$%g$"
is often desirable.  If the empty string "" is used, no label will be
plotted with each tic, though the tic mark will still be plotted.  To
eliminate all tic marks, use `unset xtics` or @ref{ytics}.

Newline (\n) is accepted in the format string.  Use double-quotes rather than
single-quotes to enable such interpretation.  See also `syntax`.

The default format for both axes is "% g", but other formats such as "%.2f" or
"%3.0em" are often desirable.  Anything accepted by 'printf' when given a
double precision number, and accepted by the terminal, will work.  Some other
options have been added.  If the format string looks like a floating point
format, then `gnuplot` tries to construct a reasonable format.

Characters not preceded by "%" are printed verbatim.  Thus you can include
spaces and labels in your format string, such as "%g m", which will put " m"
after each number.  If you want "%" itself, double it: "%g %%".

See also `set xtics` for more information about tic labels, and
@ref{decimalsign} for how to use non-default decimal separators in numbers
printed this way.
See also
@uref{http://www.gnuplot.info/demo/electron.html,electron demo (electron.dem).
}

@menu
* gprintf_::                    
* format_specifiers::           
* time/date_specifiers::        
@end menu

@node gprintf_, format_specifiers, format_, format_
@subsubsection gprintf

@cindex gprintf
@findex gprintf


The string function gprintf("format",x) uses gnuplot's own format specifiers,
as do the gnuplot commands `set format`, @ref{timestamp}, and others. These
format specifiers are not the same as those used by the standard C-language
routine sprintf(). Gnuplot also provides an sprintf("format",x,...) routine
if you prefer. For a list of gnuplot's format options, see `format specifiers`.

@node format_specifiers, time/date_specifiers, gprintf_, format_
@subsubsection format specifiers

@c ?commands set format specifiers
@c ?set format specifiers
@c ?format specifiers
@cindex format_specifiers

The acceptable formats (if not in time/date mode) are:


@example
      Format       Explanation
      %f           floating point notation
      %e or %E     exponential notation; an "e" or "E" before the power
      %g or %G     the shorter of %e (or %E) and %f
      %x or %X     hex
      %o or %O     octal
      %t           mantissa to base 10
      %l           mantissa to base of current logscale
      %s           mantissa to base of current logscale; scientific power
      %T           power to base 10
      %L           power to base of current logscale
      %S           scientific power
      %c           character replacement for scientific power
      %P           multiple of pi

@end example


A 'scientific' power is one such that the exponent is a multiple of three.
Character replacement of scientific powers (`"%c"`) has been implemented
for powers in the range -18 to +18.  For numbers outside of this range the
format reverts to exponential.

Other acceptable modifiers (which come after the "%" but before the format
specifier) are "-", which left-justifies the number; "+", which forces all
numbers to be explicitly signed; " " (a space), which makes positive numbers
have a space in front of them where negative numbers have "-";
"#", which places a decimal point after
floats that have only zeroes following the decimal point; a positive integer,
which defines the field width; "0" (the digit, not the letter) immediately
preceding the field width, which indicates that leading zeroes are to be used
instead of leading blanks; and a decimal point followed by a non-negative
integer, which defines the precision (the minimum number of digits of an
integer, or the number of digits following the decimal point of a float).

Some systems may not support all of these modifiers but may also support
others; in case of doubt, check the appropriate documentation and
then experiment.

Examples:
@example
      set format y "%t"; set ytics (5,10)          # "5.0" and "1.0"
      set format y "%s"; set ytics (500,1000)      # "500" and "1.0"
      set format y "%+-12.3f"; set ytics(12345)    # "+12345.000  "
      set format y "%.2t*10^%+03T"; set ytic(12345)# "1.23*10^+04"
      set format y "%s*10^@{%S@}"; set ytic(12345)   # "12.345*10^@{3@}"
      set format y "%s %cg"; set ytic(12345)       # "12.345 kg"
      set format y "%.0P pi"; set ytic(6.283185)   # "2 pi"
      set format y "%.0f%%"; set ytic(50)          # "50%"

@end example

@example
      set log y 2; set format y '%l'; set ytics (1,2,3)
      #displays "1.0", "1.0" and "1.5" (since 3 is 1.5 * 2^1)

@end example

There are some problem cases that arise when numbers like 9.999 are printed
with a format that requires both rounding and a power.

If the data type for the axis is time/date, the format string must contain
valid codes for the 'strftime' function (outside of `gnuplot`, type "man
strftime").  See @ref{timefmt} for a list of the allowed input format codes.

@node time/date_specifiers,  , format_specifiers, format_
@subsubsection time/date specifiers

@c ?commands set format date_specifiers
@c ?commands set format time_specifiers
@c ?set format date_specifiers
@c ?set format time_specifiers
@c ?set date_specifiers
@c ?set time_specifiers
@cindex date_specifiers

@cindex time_specifiers

In time/date mode, the acceptable formats are:


@example
      Format       Explanation
      %a           abbreviated name of day of the week
      %A           full name of day of the week
      %b or %h     abbreviated name of the month
      %B           full name of the month
      %d           day of the month, 01--31
      %D           shorthand for "%m/%d/%y" (only output)
      %F           shorthand for "%Y-%m-%d" (only output)
      %k           hour, 0--23 (one or two digits)
      %H           hour, 00--23 (always two digits)
      %l           hour, 1--12 (one or two digits)
      %I           hour, 01--12 (always two digits)
      %j           day of the year, 1--366
      %m           month, 01--12
      %M           minute, 0--60
      %p           "am" or "pm"
      %r           shorthand for "%I:%M:%S %p" (only output)
      %R           shorthand for "%H:%M" (only output)
      %S           second, 0--60
      %T           shorthand for "%H:%M:%S" (only output)
      %U           week of the year (week starts on Sunday)
      %w           day of the week, 0--6 (Sunday = 0)
      %W           week of the year (week starts on Monday)
      %y           year, 0-99
      %Y           year, 4-digit

@end example


Except for the non-numerical formats, these may be preceded by a "0" ("zero",
not "oh") to pad the field length with leading zeroes, and a positive digit,
to define the minimum field width (which will be overridden if the specified
width is not large enough to contain the number).  There is a 24-character
limit to the length of the printed text; longer strings will be truncated.

Examples:

Suppose the text is "76/12/25 23:11:11".  Then
@example
      set format x                 # defaults to "12/25/76" \n "23:11"
      set format x "%A, %d %b %Y"  # "Saturday, 25 Dec 1976"
      set format x "%r %D"         # "11:11:11 pm 12/25/76"

@end example

Suppose the text is "98/07/06 05:04:03".  Then
@example
      set format x "%1y/%2m/%3d %01H:%02M:%03S"  # "98/ 7/  6 5:04:003"

@end example

@node function_style, functions, format_, set-show
@subsection function style

This form of the command is deprecated. Please see `set style function`.

@node functions, grid, function_style, set-show
@subsection functions

@c ?commands show functions
@c ?show functions
The @ref{functions} command lists all user-defined functions and their
definitions.

Syntax:
@example
      show functions

@end example

For information about the definition and usage of functions in `gnuplot`,
please see `expressions`.
See also
@uref{http://www.gnuplot.info/demo/spline.html,splines as user defined functions (spline.dem)
}
and
@uref{http://www.gnuplot.info/demo/airfoil.html,use of functions and complex variables for airfoils (airfoil.dem).
}

@node grid, hidden3d, functions, set-show
@subsection grid

@c ?commands set grid
@c ?commands unset grid
@c ?commands show grid
@c ?set grid
@c ?unset grid
@c ?show grid
@cindex grid
@opindex grid


@cindex nogrid

The `set grid` command allows grid lines to be drawn on the plot.

Syntax:
@example
      set grid @{@{no@}@{m@}xtics@} @{@{no@}@{m@}ytics@} @{@{no@}@{m@}ztics@}
               @{@{no@}@{m@}x2tics@} @{@{no@}@{m@}y2tics@}
               @{@{no@}@{m@}cbtics@}
               @{polar @{<angle>@}@}
               @{layerdefault | front | back@}
               @{ @{linestyle <major_linestyle>@}
                 | @{linetype | lt <major_linetype>@}
                   @{linewidth | lw <major_linewidth>@}
                 @{ , @{linestyle | ls <minor_linestyle>@}
                     | @{linetype | lt <minor_linetype>@}
                       @{linewidth | lw <minor_linewidth>@} @} @}
      unset grid
      show grid

@end example

The grid can be enabled and disabled for the major and/or minor tic
marks on any axis, and the linetype and linewidth can be specified
for major and minor grid lines, also via a predefined linestyle, as
far as the active terminal driver supports this.

Additionally, a polar grid can be selected for 2-d plots---circles are drawn
to intersect the selected tics, and radial lines are drawn at definable
intervals.  (The interval is given in degrees or radians, depending on the
@ref{angles} setting.)  Note that a polar grid is no longer automatically
generated in polar mode.

The pertinent tics must be enabled before `set grid` can draw them; `gnuplot`
will quietly ignore instructions to draw grid lines at non-existent tics, but
they will appear if the tics are subsequently enabled.

If no linetype is specified for the minor gridlines, the same linetype as the
major gridlines is used.  The default polar angle is 30 degrees.

If `front` is given, the grid is drawn on top of the graphed data. If
`back` is given, the grid is drawn underneath the graphed data. Using
`front` will prevent the grid from being obscured by dense data. The
default setup, `layerdefault`, is equivalent to `back` for 2d plots.
In 3D plots the default is to split up the grid and the graph box into
two layers: one behind, the other in front of the plotted data and
functions. Since @ref{hidden3d} mode does its own sorting, it ignores
all grid drawing order options and passes the grid lines through the
hidden line removal machinery instead. These options actually affect
not only the grid, but also the lines output by @ref{border} and the
various ticmarks (see `set xtics`).

Z grid lines are drawn on the bottom of the plot.  This looks better if a
partial box is drawn around the plot---see @ref{border}.

@node hidden3d, historysize, grid, set-show
@subsection hidden3d

@c ?commands set hidden3d
@c ?commands unset hidden3d
@c ?commands show hidden3d
@c ?set hidden3d
@c ?unset hidden3d
@c ?show hidden3d
@cindex hidden3d
@opindex hidden3d


@cindex nohidden3d

The @ref{hidden3d} command enables hidden line removal for surface plotting
(see `splot`).  Some optional features of the underlying algorithm can also
be controlled using this command.

Syntax:
@example
      set hidden3d @{defaults@} |
                   @{ @{@{offset <offset>@} | @{nooffset@}@}
                     @{trianglepattern <bitpattern>@}
                     @{@{undefined <level>@} | @{noundefined@}@}
                     @{@{no@}altdiagonal@}
                     @{@{no@}bentover@} @}
      unset hidden3d
      show hidden3d

@end example

In contrast to the usual display in gnuplot, hidden line removal actually
treats the given function or data grids as real surfaces that can't be seen
through, so parts behind the surface will be hidden by it.  For this to be
possible, the surface needs to have 'grid structure' (see @ref{datafile}
about this), and it has to be drawn `with lines` or `with linespoints`.

When @ref{hidden3d} is set, both the hidden portion of the surface and possibly
its contours drawn on the base (see @ref{contour}) as well as the grid will
be hidden.  Each surface has its hidden parts removed with respect to itself
and to other surfaces, if more than one surface is plotted.  Contours drawn
on the surface (@ref{surface}) don't work.

Labels and arrows are always visible and are unaffected.  The key box is
never hidden by the surface. As of gnuplot version 4.2, @ref{hidden3d} also
affects 3D plotting styles `with points`, `with labels`, and `with vectors`,
even if no surface is present in the graph.  Individual plots within the
graph may be explicitly excluded from this processing by appending the extra
option `nohidden3d` to the @ref{with} specifier.

Hidden3d does not affect solid surfaces drawn using the pm3d mode. To
achieve a similar effect for pm3d surfaces, use instead set @ref{depthorder}.

Functions are evaluated at isoline intersections.  The algorithm interpolates
linearly between function points or data points when determining the visible
line segments.  This means that the appearance of a function may be different
when plotted with @ref{hidden3d} than when plotted with `nohidden3d` because in
the latter case functions are evaluated at each sample.  Please see
@ref{samples} and @ref{isosamples} for discussion of the difference.

The algorithm used to remove the hidden parts of the surfaces has some
additional features controllable by this command.  Specifying `defaults` will
set them all to their default settings, as detailed below.  If `defaults` is
not given, only explicitly specified options will be influenced: all others
will keep their previous values, so you can turn on/off hidden line removal
via `set @{no@}hidden3d`, without modifying the set of options you chose.

The first option, `offset`, influences the linestyle used for lines on the
'back' side.  Normally, they are drawn in a linestyle one index number higher
than the one used for the front, to make the two sides of the surface
distinguishable.  You can specify a different line style offset to add
instead of the default 1, by `offset <offset>`.  Option `nooffset` stands for
`offset 0`, making the two sides of the surface use the same linestyle.

Next comes the option `trianglepattern <bitpattern>`.  <bitpattern> must be
a number between 0 and 7, interpreted as a bit pattern.  Each bit determines
the visibility of one edge of the triangles each surface is split up into.
Bit 0 is for the 'horizontal' edges of the grid, Bit 1 for the 'vertical'
ones, and Bit 2 for the diagonals that split each cell of the original grid
into two triangles.  The default pattern is 3, making all horizontal and
vertical lines visible, but not the diagonals.  You may want to choose 7 to
see those diagonals as well.

The `undefined <level>` option lets you decide what the algorithm is to do
with data points that are undefined (missing data, or undefined function
values), or exceed the given x-, y- or z-ranges.  Such points can either be
plotted nevertheless, or taken out of the input data set.  All surface
elements touching a point that is taken out will be taken out as well, thus
creating a hole in the surface.  If <level> = 3, equivalent to option
`noundefined`, no points will be thrown away at all.  This may produce all
kinds of problems elsewhere, so you should avoid this.  <level> = 2 will
throw away undefined points, but keep the out-of-range ones.  <level> = 1,
the default, will get rid of out-of-range points as well.

By specifying `noaltdiagonal`, you can override the default handling of a
special case can occur if `undefined` is active (i.e. <level> is not 3).
Each cell of the grid-structured input surface will be divided in two
triangles along one of its diagonals.  Normally, all these diagonals have
the same orientation relative to the grid.  If exactly one of the four cell
corners is excluded by the `undefined` handler, and this is on the usual
diagonal, both triangles will be excluded.  However if the default setting
of `altdiagonal` is active, the other diagonal will be chosen for this cell
instead, minimizing the size of the hole in the surface.

The `bentover` option controls what happens to another special case, this
time in conjunction with the `trianglepattern`.  For rather crumply surfaces,
it can happen that the two triangles a surface cell is divided into are seen
from opposite sides (i.e. the original quadrangle is 'bent over'), as
illustrated in the following ASCII art:

@example
                                                              C----B
    original quadrangle:  A--B      displayed quadrangle:     |\   |
      ("set view 0,0")    | /|    ("set view 75,75" perhaps)  | \  |
                          |/ |                                |  \ |
                          C--D                                |   \|
                                                              A    D

@end example

If the diagonal edges of the surface cells aren't generally made visible by
bit 2 of the <bitpattern> there, the edge CB above wouldn't be drawn at all,
normally, making the resulting display hard to understand.  Therefore, the
default option of `bentover` will turn it visible in this case.  If you don't
want that, you may choose `nobentover` instead.
See also
@uref{http://www.gnuplot.info/demo/hidden.html,hidden line removal demo (hidden.dem)
}
and
@uref{http://www.gnuplot.info/demo/singulr.html,complex hidden line demo (singulr.dem).
}

@node historysize, isosamples, hidden3d, set-show
@subsection historysize

@c ?commands set historysize
@c ?set historysize
@c ?unset historysize
@cindex historysize
@opindex historysize


@cindex nohistorysize

Note: the command @ref{historysize} is only available when
gnuplot has been configured with the GNU readline.

Syntax:
@example
      set historysize <int>
      unset historysize

@end example

When leaving gnuplot, the value of historysize is used for
truncating the history to at most that much lines. The default
is 500.
@ref{historysize} will disable history truncation and thus
allow an infinite number of lines to be written to the history
file.

@node isosamples, key, historysize, set-show
@subsection isosamples

@c ?commands set isosamples
@c ?commands show isosamples
@c ?set isosamples
@c ?show isosamples
@cindex isosamples
@opindex isosamples


The isoline density (grid) for plotting functions as surfaces may be changed
by the @ref{isosamples} command.

Syntax:
@example
      set isosamples <iso_1> @{,<iso_2>@}
      show isosamples

@end example

Each function surface plot will have <iso_1> iso-u lines and <iso_2> iso-v
lines.  If you only specify <iso_1>, <iso_2> will be set to the same value
as <iso_1>.  By default, sampling is set to 10 isolines per u or v axis.
A higher sampling rate will produce more accurate plots, but will take longer.
These parameters have no effect on data file plotting.

An isoline is a curve parameterized by one of the surface parameters while
the other surface parameter is fixed.  Isolines provide a simple means to
display a surface.  By fixing the u parameter of surface s(u,v), the iso-u
lines of the form c(v) = s(u0,v) are produced, and by fixing the v parameter,
the iso-v lines of the form c(u) = s(u,v0) are produced.

When a function surface plot is being done without the removal of hidden
lines, @ref{samples}  controls the number of points sampled along each
isoline;  see @ref{samples} and @ref{hidden3d}. The contour algorithm
assumes that a function sample occurs at each isoline intersection, so
change in @ref{samples} as well as @ref{isosamples} may be desired when changing
the resolution of a function surface/contour.

@node key, label, isosamples, set-show
@subsection key

@c ?commands set key
@c ?commands unset key
@c ?commands show key
@c ?set key
@c ?unset key
@c ?show key
@cindex key
@opindex key


@cindex nokey

@cindex legend

The @ref{key} command enables a key (or legend) describing plots on a plot.

The contents of the key, i.e., the names given to each plotted data set and
function and samples of the lines and/or symbols used to represent them, are
determined by the @ref{title} and @ref{with} options of the @{`s`@}`plot` command.
Please see @ref{title} and @ref{with} for more information.

Syntax:
@example
      set key @{on|off@} @{default@}
              @{@{inside | outside@} | @{lmargin | rmargin | tmargin | bmargin@}
                | @{at <position>@}@}
              @{left | right | center@} @{top | bottom | center@}
              @{vertical | horizontal@} @{Left | Right@}
              @{@{no@}reverse@} @{@{no@}invert@}
              @{samplen <sample_length>@} @{spacing <vertical_spacing>@}
              @{width <width_increment>@}
              @{height <height_increment>@}
              @{@{no@}autotitle @{columnheader@}@}
              @{title "<text>"@} @{@{no@}enhanced@}
              @{@{no@}box @{ @{linestyle | ls <line_style>@}
                         | @{linetype | lt <line_type>@}
                           @{linewidth | lw <line_width>@}@}@}
      unset key
      show key

@end example

Plots may be drawn with no visible key by requesting `set key off` or
@ref{key}.

Elements within the key are stacked according to `vertical` or `horizontal`.
In the case of `vertical`, the key occupies as few columns as possible.  That
is, elements are aligned in a column until running out of vertical space at
which point a new column is started.  In the case of `horizontal`, the key
occupies as few rows as possible.

By default the key is placed in the upper right inside corner of the graph.
The keywords `left`, `right`, `top`, `bottom`, `center`, `inside`, `outside`,
@ref{lmargin}, @ref{rmargin}, @ref{tmargin}, @ref{bmargin} (, `above`, `over`, `below` and
`under`) may be used to automatically place the key in other positions of the
graph.  Also an `at <position>` may be given to indicate precisely where the
plot should be placed.  In this case, the keywords `left`, `right`, `top`,
`bottom` and `center` serve an analogous purpose for alignment.

To understand positioning, the best concept is to think of a region, i.e.,
inside/outside, or one of the margins.  Along with the region, keywords
`left/center/right` (l/c/r) and `top/center/bottom` (t/c/b) control where
within the particular region the key should be placed.

When in `inside` mode, the keywords `left` (l), `right` (r), `top` (t),
`bottom` (b), and `center` (c) push the key out toward the plot boundary as
illustrated:

@example
     t/l   t/c   t/r

@end example

@example
     c/l    c    c/r

@end example

@example
     b/l   b/c   b/r

@end example


When in `outside` mode, automatic placement is similar to the above
illustration, but with respect to the view, rather than the graph boundary.
That is, a border is moved inward to make room for the key outside of
the plotting area, although this may interfere with other labels and may
cause an error on some devices.  The particular plot border that is moved
depends upon the position described above and the stacking direction.  For
options centered in one of the dimensions, there is no ambiguity about which
border to move.  For the corners, when the stack direction is `vertical`, the
left or right border is moved inward appropriately.  When the stack direction
is `horizontal`, the top or bottom border is moved inward appropriately.

The margin syntax allows automatic placement of key regardless of stack
direction.  When one of the margins @ref{lmargin} (lm), @ref{rmargin} (rm),
@ref{tmargin} (tm), and @ref{bmargin} (bm) is combined with a single, non-conflicting
direction keyword, the following illustrated positions may contain the key:

@example
          l/tm  c/tm  r/tm

@end example

@example
     t/lm                  t/rm

@end example

@example
     c/lm                  c/rm

@end example

@example
     b/lm                  b/rm

@end example

@example
          l/bm  c/bm  r/bm

@end example


Keywords `above` and `over` are synonymous with @ref{tmargin}.  For version
compatibility, `above` or `over` without an additional l/c/r or stack direction
keyword uses `center` and `horizontal`.  Keywords `below` and `under` are
synonymous with @ref{bmargin}.  For compatibility, `below` or `under` without an
additional l/c/r or stack  direction keyword uses `center` and `horizontal`.  A
further compatibility issue is that `outside` appearing without an additional
t/b/c or stack direction keyword uses `top`, `right` and `vertical` (i.e., the
same as t/rm above).

The <position> can be a simple x,y,z as in previous versions, but these can
be preceded by one of five keywords (`first`, `second`, `graph`, `screen`,
`character`) which selects the coordinate system in which the position of
the first sample line is specified.  See `coordinates` for more details.
The effect of `left`, `right`, `top`, `bottom`, and `center` when <position>
is given is to align the key as though it were text positioned using the
label command, i.e., `left` means left align with key to the right of
<position>, etc.

Justification of the labels within the key is controlled by `Left` or `Right`
(default is `Right`).  The text and sample can be reversed (`reverse`) and a
box can be drawn around the key (`box @{...@}`) in a specified `linetype`
and `linewidth`, or a user-defined `linestyle`. Note that not all
terminal drivers support linewidth selection, though.

By default the first plot label is at the top of the key and successive labels
are entered below it. The `invert` option causes the first label to be placed
at the bottom of the key, with successive labels entered above it. This option
is useful to force the vertical ordering of labels in the key to match the
order of box types in a stacked histogram.

The length of the sample line can be controlled by `samplen`.  The sample
length is computed as the sum of the tic length and <sample_length> times the
character width.  `samplen` also affects the positions of point samples in
the key since these are drawn at the midpoint of the sample line, even if
the sample line itself is not drawn.

The vertical spacing between lines is controlled by `spacing`.  The spacing
is set equal to the product of the pointsize, the vertical tic size, and
<vertical_spacing>.  The program will guarantee that the vertical spacing is
no smaller than the character height.

The <width_increment> is a number of character widths to be added to or
subtracted from the length of the string.  This is useful only when you are
putting a box around the key and you are using control characters in the text.
`gnuplot` simply counts the number of characters in the string when computing
the box width; this allows you to correct it.

The <height_increment> is a number of character heights to be added to or
subtracted from the height of the key box.  This is useful mainly when you are
putting a box around the key, otherwise it can be used to adjust the vertical
shift of automatically chosen key position by <height_increment>/2.

All plotted curves of `plot`s and `splot`s are titled according to the
default option `autotitles`. The automatic generation of titles can be
suppressed by `noautotitles`; then only those titles explicitly defined
by `(s)plot ... title ...` will be drawn.

The `set key autotitle columnheader` option is available if gnuplot was built
with --enable-datastrings. This command causes the first entry in each column
of plotted data to be interpreted as a text string and used as a title for
the corresponding plot. If the quantity being plotted is a function of data
from several columns, gnuplot may be confused as to which column to draw the
title from. In this case it is necessary to specify the column explicitly in
the plot command, e.g. `plot "datafile" using (($2+$3)/$4) title 3 with lines`.

A title can be put on the key (`title "<text>"`)---see also `syntax` for the
distinction between text in single- or double-quotes.  The key title uses the
same justification as do the plot titles.

An explicitly given title is typeset using enhanced text properties on
terminals supporting this, see `enhanced text` for more details.
This default behavior can be switched off by the `noenhanced` option.

The defaults for @ref{key} are `on`, `right`, `top`, `vertical`, `Right`,
`noreverse`, `noinvert`, `samplen 4`, `spacing 1.25`, `title ""`, and
`nobox`.  The default <linetype> is the same as that used for the plot
borders.  Entering `set key default` returns the key to its default
configuration.

The key is drawn as a sequence of lines, with one plot described on each
line.  On the right-hand side (or the left-hand side, if `reverse` is
selected) of each line is a representation that attempts to mimic the way the
curve is plotted.  On the other side of each line is the text description
(the line title), obtained from the `plot` command.  The lines are vertically
arranged so that an imaginary straight line divides the left- and right-hand
sides of the key.  It is the coordinates of the top of this line that are
specified with the @ref{key} command.  In a `plot`, only the x and y
coordinates are used to specify the line position.  For a `splot`, x, y and
z are all used as a 3-d location mapped using the same mapping as the graph
itself to form the required 2-d screen position of the imaginary line.

When using the TeX or PostScript drivers, or similar drivers where formatting
information is embedded in the string, `gnuplot` is unable to calculate
correctly the width of the string for key positioning.  If the key is to be
positioned at the left, it may be convenient to use the combination  `set key
left Left reverse`.  The box and gap in the grid will be the width of the
literal string.

If `splot` is being used to draw contours, the contour labels will be listed
in the key.  If the alignment of these labels is poor or a different number
of decimal places is desired, the label format can be specified.  See
@ref{clabel} for details.

Examples:

This places the key at the default location:
@example
      set key default

@end example

This disables the key:
@example
      unset key

@end example

This places a key at coordinates 2,3.5,2 in the default (first) coordinate
system:
@example
      set key at 2,3.5,2

@end example

This places the key below the graph:
@example
      set key below

@end example

This places the key in the bottom left corner, left-justifies the text,
gives it a title, and draws a box around it in linetype 3:
@example
      set key left bottom Left title 'Legend' box 3

@end example

@node label, lmargin, key, set-show
@subsection label

@c ?commands set label
@c ?commands unset label
@c ?commands show label
@c ?set label
@c ?unset label
@c ?show label
@cindex label
@opindex label


@cindex nolabel

Arbitrary labels can be placed on the plot using the @ref{label} command.

Syntax:
@example
      set label @{<tag>@} @{"<label text>"@} @{at <position>@}
                @{left | center | right@}
                @{norotate | rotate @{by <degrees>@}@}
                @{font "<name>@{,<size>@}"@}
                @{noenhanced@}
                @{front | back@}
                @{textcolor <colorspec>@}
                @{point <pointstyle> | nopoint@}
                @{offset <offset>@}
      unset label @{<tag>@}
      show label

@end example

The <position> is specified by either x,y or x,y,z, and may be preceded by
`first`, `second`, `graph`, `screen`, or `character` to select the coordinate
system.  See `coordinates` for details.

The tag is an integer that is used to identify the label. If no <tag>
is given, the lowest unused tag value is assigned automatically.  The
tag can be used to delete or modify a specific label.  To change any
attribute of an existing label, use the @ref{label} command with the
appropriate tag, and specify the parts of the label to be changed.

The <label text> can be a string constant, a string variable, or a string-
valued expression. See `strings`, @ref{sprintf}, and @ref{gprintf}.

By default, the text is placed flush left against the point x,y,z.  To adjust
the way the label is positioned with respect to the point x,y,z, add the
justification parameter, which may be `left`, `right` or `center`,
indicating that the point is to be at the left, right or center of the text.
Labels outside the plotted boundaries are permitted but may interfere with
axis labels or other text.

If `rotate` is given, the label is written vertically (if the terminal can do
so, of course).  If `rotate by <degrees>` is given, conforming terminals will
try to write the text at the specified angle; non-conforming terminals will
treat this as vertical text.

Font and its size can be chosen explicitly by `font "<name>@{,<size>@}"` if the
terminal supports font settings.  Otherwise the default font of the terminal
will be used.

Normally the enhanced text mode string interpretation, if enabled for the
current terminal, is applied to all text strings including label text.
The `noenhanced` property can be used to exempt a specific label from the
enhanced text mode processing.  The can be useful if the label contains
underscores, for example. See `enhanced text`.

If `front` is given, the label is written on top of the graphed data. If
`back` is given (the default), the label is written underneath the graphed
data.  Using `front` will prevent a label from being obscured by dense data.

`textcolor <colorspec>` changes the color of the label text. <colorspec> can be
a linetype, an rgb color, or a palette mapping. See help for @ref{colorspec} and
@ref{palette}.  `textcolor` may be abbreviated `tc`.
@example
   `tc default` resets the text color to its default state.
   `tc lt <n>` sets the text color to that of line type <n>.
   `tc ls <n>` sets the text color to that of line style <n>.
   `tc palette z` selects a palette color corresponding to the label z position.
   `tc palette cb <val>` selects a color corresponding to <val> on the colorbar.
   `tc palette fraction <val>`, with 0<=val<=1, selects a color corresponding to
       the mapping [0:1] to grays/colors of the @ref{palette}.
   `tc rgb "#RRGGBB"` selects an arbitrary 24-bit RGB color.

@end example

If a <pointstyle> is given, using keywords `lt`, `pt` and `ps`, see @ref{style},
a point with the given style and color of the given line type is plotted at
the label position and the text of the label is displaced slightly.
This option is used by default for placing labels in `mouse` enhanced
terminals.  Use `nopoint` to turn off the drawing of a point near
the label (this is the default).

The displacement defaults to 1,1 in @ref{pointsize} units if a <pointstyle> is
given, 0,0 if no <pointstyle> is given.  The displacement can be controlled
by the optional `offset <offset>` where <offset> is specified by either x,y
or x,y,z, and may be preceded by `first`, `second`, `graph`, `screen`, or
`character` to select the coordinate system.  See `coordinates` for details.

If one (or more) axis is timeseries, the appropriate coordinate should be
given as a quoted time string according to the @ref{timefmt} format string.
See @ref{xdata} and @ref{timefmt}.

The EEPIC, Imagen, LaTeX, and TPIC drivers allow \\ in a string to specify
a newline.

Examples:

To set a label at (1,2) to "y=x", use:
@example
      set label "y=x" at 1,2

@end example

To set a Sigma of size 24, from the Symbol font set, at the center of
the graph, use:
@example
      set label "S" at graph 0.5,0.5 center font "Symbol,24"

@end example

To set a label "y=x^2" with the right of the text at (2,3,4), and tag the
label as number 3, use:
@example
      set label 3 "y=x^2" at 2,3,4 right

@end example

To change the preceding label to center justification, use:
@example
      set label 3 center

@end example

To delete label number 2, use:
@example
      unset label 2

@end example

To delete all labels, use:
@example
      unset label

@end example

To show all labels (in tag order), use:
@example
      show label

@end example

To set a label on a graph with a timeseries on the x axis, use, for example:
@example
      set timefmt "%d/%m/%y,%H:%M"
      set label "Harvest" at "25/8/93",1

@end example

To display a freshly fitted parameter on the plot with the data and the
fitted function, do this after the @ref{fit}, but before the `plot`:
@example
      set label sprintf("a = %3.5g",par_a) at 30,15
      bfit = gprintf("b = %s*10^%S",par_b)
      set label bfit at 30,20

@end example

To set a label displaced a little bit from a small point:
@example
      set label 'origin' at 0,0 point lt 1 pt 2 ps 3 offset 1,-1

@end example

To set a label whose color matches the z value (in this case 5.5) of some
point on a 3D splot colored using pm3d:
@example
      set label 'text' at 0,0,5.5 tc palette z

@end example


@node lmargin, loadpath, label, set-show
@subsection lmargin

@c ?commands set lmargin
@c ?set lmargin
@cindex lmargin
@opindex lmargin


The command @ref{lmargin} sets the size of the left margin.
Please see @ref{margin} for details.

@node loadpath, locale, lmargin, set-show
@subsection loadpath

@c ?commands set loadpath
@c ?commands show loadpath
@c ?set loadpath
@c ?show loadpath
@cindex loadpath
@opindex loadpath


The @ref{loadpath} setting defines additional locations for data and command
files searched by the @ref{call}, `load`, `plot` and `splot` commands.  If a
file cannot be found in the current directory, the directories in
@ref{loadpath} are tried.

Syntax:
@example
      set loadpath @{"pathlist1" @{"pathlist2"...@}@}
      show loadpath

@end example

Path names may be entered as single directory names, or as a list of
path names separated by a platform-specific path separator, eg. colon
(':') on Unix, semicolon (';') on DOS/Windows/OS/2/Amiga platforms.
The @ref{loadpath}, @ref{save} and `save set` commands replace the
platform-specific separator with a space character (' ') for maximum
portability.

If the environment variable GNUPLOT_LIB is set, its contents are
appended to @ref{loadpath}.  However, @ref{loadpath} prints the contents
of user defined loadpath and system loadpath separately.  Also, the
@ref{save} and `save set` commands save only the user specified parts of
@ref{loadpath}, for portability reasons.

@node locale, logscale, loadpath, set-show
@subsection locale

@c ?commands set locale
@c ?set locale
@cindex locale
@opindex locale


The @ref{locale} setting determines the language with which `@{x,y,z@}@{d,m@}tics`
will write the days and months.

Syntax:
@example
      set locale @{"<locale>"@}

@end example

<locale> may be any language designation acceptable to your installation.
See your system documentation for the available options.  The default value
is determined from the LC_TIME, LC_ALL, or LANG environment variables.

To change the decimal point locale, see @ref{decimalsign}.

@node logscale, macros, locale, set-show
@subsection logscale

@c ?commands set logscale
@c ?commands unset logscale
@c ?commands show logscale
@c ?set logscale
@c ?unset logscale
@c ?show logscale
@c ?set log
@cindex logscale
@opindex logscale


@cindex nologscale

Syntax:
@example
      set logscale <axes> <base>
      unset logscale <axes>
      show logscale

@end example

where <axes> may be any combination of `x`, `x2`, `y`, `y2`, `z`, and `cb` in
any order, and where <base> is the base of the log scaling.  If <base> is not
given, then 10 is assumed.  If <axes> is not given, then all axes are assumed.
@ref{logscale} turns off log scaling for the specified axes.

Examples:

To enable log scaling in both x and z axes:
@example
      set logscale xz

@end example

To enable scaling log base 2 of the y axis:
@example
      set logscale y 2

@end example

To enable z and color log axes for a pm3d plot:
@example
      set logscale zcb

@end example

To disable z axis log scaling:
@example
      unset logscale z

@end example

@node macros, mapping, logscale, set-show
@subsection macros

@c ?commands set macros
@c ?commands show macros
@c ?set macros
@c ?show macros
If command line macro substitution is enabled, then tokens in the command line
of the form @@<stringvariablename> will be replaced by the text string contained
in <stringvariablename>. See `substitution`.

Syntax:
@example
     set macros

@end example


@node mapping, margin, macros, set-show
@subsection mapping

@c ?commands set mapping
@c ?commands show mapping
@c ?set mapping
@c ?show mapping
@cindex mapping
@opindex mapping


If data are provided to `splot` in spherical or cylindrical coordinates,
the @ref{mapping} command should be used to instruct `gnuplot` how to
interpret them.

Syntax:
@example
      set mapping @{cartesian | spherical | cylindrical@}

@end example

A cartesian coordinate system is used by default.

For a spherical coordinate system, the data occupy two or three columns
(or @ref{using} entries).  The first two are interpreted as the azimuthal
and polar angles theta and phi (or "longitude" and "latitude"), in the
units specified by @ref{angles}.  The radius r is taken from the third
column if there is one, or is set to unity if there is no third column.
The mapping is:

@example
      x = r * cos(theta) * cos(phi)
      y = r * sin(theta) * cos(phi)
      z = r * sin(phi)

@end example

Note that this is a "geographic" spherical system, rather than a "polar"
one (that is, phi is measured from the equator, rather than the pole).

For a cylindrical coordinate system, the data again occupy two or three
columns.  The first two are interpreted as theta (in the units specified by
@ref{angles}) and z.  The radius is either taken from the third column or set
to unity, as in the spherical case.  The mapping is:

@example
      x = r * cos(theta)
      y = r * sin(theta)
      z = z

@end example

The effects of @ref{mapping} can be duplicated with the @ref{using} filter on the
`splot` command, but @ref{mapping} may be more convenient if many data files are
to be processed.  However even if @ref{mapping} is used, @ref{using} may still be
necessary if the data in the file are not in the required order.

@ref{mapping} has no effect on `plot`.
@c ^ See also
@uref{http://www.gnuplot.info/demo/world.html,world.dem: mapping demos.
}

@node margin, mouse, mapping, set-show
@subsection margin

@c ?commands set margin
@c ?commands show margin
@c ?set margin
@c ?show margin
@cindex margin
@opindex margin


The computed margins can be overridden by the @ref{margin} commands.  @ref{margin} shows the current settings.

Syntax:
@example
      set bmargin @{@{at screen@} <margin>@}
      set lmargin @{@{at screen@} <margin>@}
      set rmargin @{@{at screen@} <margin>@}
      set tmargin @{@{at screen@} <margin>@}
      show margin

@end example

The default units of <margin> are character heights or widths, as appropriate.
A positive value defines the absolute size of the margin.  A negative value
(or none) causes `gnuplot` to revert to the computed value.  For 3D plots,
only the left margin can be set using character units.

The keywords `at screen` indicates that the margin is specified as a fraction
of the full drawing area. This can be used to precisely line up the corners of
individual 2D and 3D graphs in a multiplot. This placement ignores the current
values of @ref{origin} and @ref{size}, and is intended as an alternative 
method for positioning graphs within a multiplot.

Normally the margins of a plot are automatically calculated based on tics,
tic labels, axis labels, the plot title, the timestamp and the size of the
key if it is outside the borders.  If, however, tics are attached to the
axes (`set xtics axis`, for example), neither the tics themselves nor their
labels will be included in either the margin calculation or the calculation
of the positions of other text to be written in the margin.  This can lead
to tic labels overwriting other text if the axis is very close to the border.

@node mouse, multiplot, margin, set-show
@subsection mouse

@c ?commands set mouse
@c ?commands unset mouse
@c ?set mouse
@c ?unset mouse
@cindex mouse
@opindex mouse


@cindex nomouse

The command `set mouse` enables mouse actions. Currently the pm, x11, ggi,
windows and wxt terminals are mouse enhanced. There are two mouse modes. The
2d-graph mode works for 2d graphs and for maps (i.e. splots with @ref{view}
having z-rotation 0, 90, 180, 270 or 360 degrees, including `set view map`)
and it allows tracing the position over graph, zooming, annotating graph etc.
For 3d graphs `splot`, the view and scaling of the graph can be changed with
mouse buttons 1 and 2. If additionally to these buttons the modifier <ctrl> is
hold down, the coordinate system only is rotated which is useful for large
data sets. A vertical motion of Button 2 with the shift key hold down changes
the @ref{ticslevel}.

Mousing is not available in multiplot mode. When multiplot is finished using
@ref{multiplot}, then the mouse will be turned on again and acts on the
last plot (like replot does).

Syntax:
@example
      set mouse @{doubleclick <ms>@} @{nodoubleclick@} \
                @{@{no@}zoomcoordinates@} \
                @{noruler | ruler @{at x,y@}@} \
                @{polardistance@{deg|tan@} | nopolardistance@} \
                @{format <string>@} \
                @{clipboardformat <int>/<string>@} \
                @{mouseformat <int>/<string>@} \
                @{@{no@}labels@} @{labeloptions <string>@} \
                @{@{no@}zoomjump@} @{@{no@}verbose@}
      unset mouse

@end example

The doubleclick resolution is given in milliseconds and used for Button 1
which copies the current mouse position to the `clipboard`. If you want that
to be done by single clicking a value of 0 ms can be used. The default value
is 300 ms.

The option `zoomcoordinates` determines if the coordinates of the zoom box are
drawn at the edges while zooming. This is on by default.

The options `noruler` and `ruler` switch the ruler off and on, the latter
optionally at given `coordinates`. This corresponds to the default key binding
'r'.

The option `polardistance` determines if the distance between the mouse cursor
and the ruler is also shown in polar coordinates (distance and angle in
degrees or tangent (slope)). This corresponds to the default key binding '5'.

The `format` option takes a fprintf like format string which determines how
floating point numbers are printed to the drivers window and the clipboard.
The default is "% #g".

`clipboardformat` and `mouseformat` are used for formatting the text on
Button1 and Button2 actions -- copying the coordinates to the clipboard and
temporarily annotating the mouse position. This corresponds to the key
bindings '1', '2', '3', '4' (see the drivers's help window). If the argument
is a string this string is used as c format specifier and should contain two
float specifiers, e.g. `set mouse mouseformat "mouse = %5.2g, %10.2f"`. Use
`set mouse mouseformat ""` to turn this string off again.

The following formats are available (format 6 may only be selected if the
format string was specified already):

@example
 0   real coordinates in  brackets e.g. [1.23, 2.45]
 1   real coordinates w/o brackets e.g.  1.23, 2.45
 2   x == timefmt                       [(as set by @ref{timefmt}), 2.45]
 3   x == date                          [31. 12. 1999, 2.45]
 4   x == time                          [23:59, 2.45]
 5   x == date / time                   [31. 12. 1999 23:59, 2.45]
 6   alt. format, specified as string   ""

@end example

Choose the option `labels` to get real gnuplot labels on Button 2. (The
default is `nolabels` which makes Button 2 drawing only temporary annotations
at the mouse positions). The labels are drawn with the current setting of
`mouseformat`. `labeloptions` controls which options are passed to the
@ref{label} command. The default is "pointstyle 1" which will plot a small
plus at the label position.  Note that the pointsize is taken from the
@ref{pointsize} command.
Labels can be removed by holding the Ctrl-Key down while clicking with
Button 2 on the label's point. The threshold for how close you must be to the
label is also determined by the @ref{pointsize}.

If the option `zoomjump` is on, the mouse pointer will be automatically
offset a small distance after starting a zoom region with button 3. This can
be useful to avoid a tiny (or even empty) zoom region. `zoomjump` is off by
default.

If the option `verbose` is turned on the communication commands are shown
during execution. This option can also be toggled by hitting `6` in the
driver's window. `verbose` is off by default.

Press 'h' in the driver's window for a short summary of the mouse and key
bindings.  This will also display user defined bindings or `hotkeys` which
can be defined using the @ref{bind} command, see help for @ref{bind}.  Note, that user
defined `hotkeys` may override the default bindings.

Press 'q' in the driver's window to close the window. This key cannot be
overridden with the @ref{bind} command.

See also help for @ref{bind} and @ref{label}.

@menu
* X11_mouse::                   
@end menu

@node X11_mouse,  , mouse, mouse
@subsubsection X11 mouse

@c ?mouse x11_mouse
@cindex x11_mouse

@c ?x11 mouse
If multiple X11 plot windows have been opened using the `set term x11 <n>`
terminal option, then only the current plot window supports the entire
range of mouse commands and hotkeys.  The other windows will, however,
continue to display mouse coordinates at the lower left.

For consistency with other screen terminals, X11 mouse support is turned on by
default, wherever the standard input comes from. However, on some UNIX
flavors, special input devices as /dev/null might not be `select-able`; using
such devices with the mouse turned on will hang gnuplot. Please turn off
mousing with `unset mouse` if you are in this situation.

@node multiplot, mx2tics, mouse, set-show
@subsection multiplot

@c ?commands set multiplot
@c ?commands unset multiplot
@c ?set multiplot
@c ?unset multiplot
@cindex multiplot
@opindex multiplot


@cindex nomultiplot

The command @ref{multiplot} places `gnuplot` in the multiplot mode, in which
several plots are placed on the same page, window, or screen.

Syntax:
@example
      set multiplot @{ layout <rows>,<cols>
                      @{rowsfirst|columnsfirst@} @{downwards|upwards@}
                      @{title <page title>@}
                      @{scale <xscale>@{,<yscale>@}@} @{offset <xoff>@{,<yoff>@}@}
                    @}
      unset multiplot

@end example

For some terminals, no plot is displayed until the command @ref{multiplot}
is given, which causes the entire page to be drawn and then returns gnuplot
to its normal single-plot mode.  For other terminals, each separate `plot`
command produces an updated display, either by redrawing all previous ones
and the newly added plot, or by just adding the new plot to the existing
display.

The area to be used by the next plot is not erased before doing the
new plot.  The @ref{clear} command can be used to do this if wanted, as is
typically the case for "inset" plots.

Any labels or arrows that have been defined will be drawn for each plot
according to the current size and origin (unless their coordinates are
defined in the `screen` system).  Just about everything else that can be
`set` is applied to each plot, too.  If you want something to appear only
once on the page, for instance a single time stamp, you'll need to put a `set
time`/`unset time` pair around one of the `plot`, `splot` or @ref{replot}
commands within the @ref{multiplot}/@ref{multiplot} block.

The multiplot title is separate from the individual plot titles, if any.
Space is reserved for it at the top of the page, spanning the full width
of the canvas.

The commands @ref{origin} and @ref{size} must be used to correctly position
each plot if no layout is specified or if fine tuning is desired.  See
@ref{origin} and @ref{size} for details of their usage.

Example:
@example
      set multiplot
      set size 0.4,0.4
      set origin 0.1,0.1
      plot sin(x)
      set size 0.2,0.2
      set origin 0.5,0.5
      plot cos(x)
      unset multiplot

@end example

This displays a plot of cos(x) stacked above a plot of sin(x).

@ref{size} and @ref{origin} refer to the entire plotting area used for each
plot.  Please also see @ref{size}.  If you want to have the axes
themselves line up, you can guarantee that the margins are the same size with
the @ref{margin} commands.  See @ref{margin} for their use.  Note that the
margin settings are absolute, in character units, so the appearance of the
graph in the remaining space will depend on the screen size of the display
device, e.g., perhaps quite different on a video display and a printer.

With the `layout` option you can generate simple multiplots without having
to give the @ref{size} and @ref{origin} commands before each plot:  Those
are generated automatically, but can be overridden at any time.  With
`layout` the display will be divided by a grid with <rows> rows and
<cols> columns.  This grid is filled rows first or columns first depending on
whether the corresponding option is given in the multiplot command.  The stack
of plots can grow `downwards` or `upwards`.
Default is `rowsfirst` and `downwards`.

Each plot can be scaled by `scale` and shifted with `offset`; if the y-values
for scale or offset are omitted, the x-value will be used.  @ref{multiplot}
will turn off the automatic layout and restore the values of @ref{size} and
@ref{origin} as they were before `set multiplot layout`.

Example:
@example
      set size 1,1
      set origin 0,0
      set multiplot layout 3,2 columnsfirst scale 1.1,0.9
      [ up to 6 plot commands here ]
      unset multiplot

@end example

The above example will produce 6 plots in 2 columns filled top to bottom,
left to right.  Each plot will have a horizontal size of 1.1/2 and a vertical
size of 0.9/3.

See also
@uref{http://gnuplot.sourceforge.net/demo/multiplt.html,multiplot demo (multiplt.dem)
}

@node mx2tics, mxtics, multiplot, set-show
@subsection mx2tics

@c ?commands set mx2tics
@c ?commands unset mx2tics
@c ?commands show mx2tics
@c ?set mx2tics
@c ?unset mx2tics
@c ?show mx2tics
@cindex mx2tics
@opindex mx2tics


@cindex nomx2tics

Minor tic marks along the x2 (top) axis are controlled by @ref{mx2tics}.
Please see @ref{mxtics}.

@node mxtics, my2tics, mx2tics, set-show
@subsection mxtics

@c ?commands set mxtics
@c ?commands unset mxtics
@c ?commands show mxtics
@c ?set mxtics
@c ?unset mxtics
@c ?show mxtics
@cindex mxtics
@opindex mxtics


@cindex nomxtics

Minor tic marks along the x axis are controlled by @ref{mxtics}.  They can be
turned off with @ref{mxtics}.  Similar commands control minor tics along
the other axes.

Syntax:
@example
      set mxtics @{<freq> | default@}
      unset mxtics
      show mxtics

@end example

The same syntax applies to @ref{mytics}, @ref{mztics}, @ref{mx2tics}, @ref{my2tics} and
`mcbtics`.

<freq> is the number of sub-intervals (NOT the number of minor tics) between
major tics (the default for a linear axis is either two or five
depending on the major tics, so there are one or four minor
tics between major tics). Selecting `default` will return the number of minor
ticks to its default value.

If the axis is logarithmic, the number of sub-intervals will be set to a
reasonable number by default (based upon the length of a decade).  This will
be overridden if <freq> is given.  However the usual minor tics (2, 3, ...,
8, 9 between 1 and 10, for example) are obtained by setting <freq> to 10,
even though there are but nine sub-intervals.

To set minor tics at arbitrary positions, use the ("<label>" <pos> <level>,
...) form of `set @{x|x2|y|y2|z@}tics` with <label> empty and <level> set to 1.

The `set m@{x|x2|y|y2|z@}tics` commands work only when there are uniformly
spaced major tics.  If all major tics were placed explicitly by
`set @{x|x2|y|y2|z@}tics`, then minor tic commands are ignored.  Implicit
major tics and explicit minor tics can be combined using
`set @{x|x2|y|y2|z@}tics` and `set @{x|x2|y|y2|z@}tics add`.

Examples:
@example
      set xtics 0, 5, 10
      set xtics add (7.5)
      set mxtics 5
@end example

Major tics at 0,5,7.5,10, minor tics at 1,2,3,4,6,7,8,9
@example
      set logscale y
      set ytics format ""
      set ytics 1e-6, 10, 1
      set ytics add ("1" 1, ".1" 0.1, ".01" 0.01, "10^-3" 0.001, \
                     "10^-4" 0.0001)
      set mytics 10
@end example

Major tics with special formatting, minor tics at log positions

By default, minor tics are off for linear axes and on for logarithmic axes.
They inherit the settings for `axis|border` and `@{no@}mirror` specified for
the major tics.  Please see `set xtics` for information about these.

@node my2tics, mytics, mxtics, set-show
@subsection my2tics

@c ?commands set my2tics
@c ?commands unset my2tics
@c ?commands show my2tics
@c ?set my2tics
@c ?unset my2tics
@c ?show my2tics
@cindex my2tics
@opindex my2tics


@cindex nomy2tics

Minor tic marks along the y2 (right-hand) axis are controlled by @ref{my2tics}.  Please see @ref{mxtics}.

@node mytics, mztics, my2tics, set-show
@subsection mytics

@c ?commands set mytics
@c ?commands unset mytics
@c ?commands show mytics
@c ?set mytics
@c ?unset mytics
@c ?show mytics
@cindex mytics
@opindex mytics


@cindex nomytics

Minor tic marks along the y axis are controlled by @ref{mytics}.  Please
see @ref{mxtics}.

@node mztics, offsets, mytics, set-show
@subsection mztics

@c ?commands set mztics
@c ?commands unset mztics
@c ?commands show mztics
@c ?set mztics
@c ?unset mztics
@c ?show mztics
@cindex mztics
@opindex mztics


@cindex nomztics

Minor tic marks along the z axis are controlled by @ref{mztics}.  Please
see @ref{mxtics}.

@node offsets, origin, mztics, set-show
@subsection offsets

@c ?commands set offsets
@c ?commands unset offsets
@c ?commands show offsets
@c ?set offsets
@c ?unset offsets
@c ?show offsets
@cindex offsets
@opindex offsets


@cindex nooffsets

Offsets provide a mechanism to put a boundary around the data inside of an
autoscaled graph.

Syntax:
@example
      set offsets <left>, <right>, <top>, <bottom>
      unset offsets
      show offsets

@end example

Each offset may be a constant or an expression.  Each defaults to 0.  Left
and right offsets are given in units of the x axis, top and bottom offsets in
units of the y axis.  A positive offset expands the graph in the specified
direction, e.g., a positive bottom offset makes ymin more negative.  Negative
offsets, while permitted, can have unexpected interactions with autoscaling
and clipping.

Offsets are ignored in `splot`s.

Example:
@example
      set offsets 0, 0, 2, 2
      plot sin(x)

@end example

This graph of sin(x) will have a y range [-3:3] because the function
will be autoscaled to [-1:1] and the vertical offsets are each two.

@node origin, output, offsets, set-show
@subsection origin

@c ?commands set origin
@c ?commands show origin
@c ?set origin
@c ?show origin
@cindex origin
@opindex origin


The @ref{origin} command is used to specify the origin of a plotting surface
(i.e., the graph and its margins) on the screen.  The coordinates are given
in the `screen` coordinate system (see `coordinates` for information about
this system).

Syntax:
@example
      set origin <x-origin>,<y-origin>

@end example

@node output, parametric_, origin, set-show
@subsection output

@c ?commands set output
@c ?commands show output
@c ?set output
@c ?show output
@cindex output
@opindex output


@c ?output file
By default, screens are displayed to the standard output. The @ref{output}
command redirects the display to the specified file or device.

Syntax:
@example
      set output @{"<filename>"@}
      show output

@end example

The filename must be enclosed in quotes.  If the filename is omitted, any
output file opened by a previous invocation of @ref{output} will be closed
and new output will be sent to STDOUT.  (If you give the command `set output
"STDOUT"`, your output may be sent to a file named "STDOUT"!  ["May be", not
"will be", because some terminals, like `x11` or `wxt`, ignore @ref{output}.])

MSDOS users should note that the \ character has special significance in
double-quoted strings, so single-quotes should be used for filenames in
different directories.

When both @ref{terminal} and @ref{output} are used together, it is safest to
give @ref{terminal} first, because some terminals set a flag which is needed
in some operating systems.  This would be the case, for example, if the
operating system needs to know whether or not a file is to be formatted in
order to open it properly.

On machines with popen functions (Unix), output can be piped through a shell
command if the first non-whitespace character of the filename is '|'.
For instance,

@example
      set output "|lpr -Plaser filename"
      set output "|lp -dlaser filename"

@end example

On MSDOS machines, `set output "PRN"` will direct the output to the default
printer.  On VMS, output can be sent directly to any spooled device.  It is
also possible to send the output to DECnet transparent tasks, which allows
some flexibility.

@node parametric_, plot_, output, set-show
@subsection parametric

@c ?commands set parametric
@c ?commands unset parametric
@c ?commands show parametric
@c ?set parametric
@c ?unset parametric
@c ?show parametric
@cindex parametric
@opindex parametric


@cindex noparametric

The `set parametric` command changes the meaning of `plot` (`splot`) from
normal functions to parametric functions.  The command `unset parametric`
restores the plotting style to normal, single-valued expression plotting.

Syntax:
@example
      set parametric
      unset parametric
      show parametric

@end example

For 2-d plotting, a parametric function is determined by a pair of parametric
functions operating on a parameter.  An example of a 2-d parametric function
would be `plot sin(t),cos(t)`, which draws a circle (if the aspect ratio is
set correctly---see @ref{size}).  `gnuplot` will display an error message if
both functions are not provided for a parametric `plot`.

For 3-d plotting, the surface is described as x=f(u,v), y=g(u,v), z=h(u,v).
Therefore a triplet of functions is required.  An example of a 3-d parametric
function would be `cos(u)*cos(v),cos(u)*sin(v),sin(u)`, which draws a sphere.
`gnuplot` will display an error message if all three functions are not
provided for a parametric `splot`.

The total set of possible plots is a superset of the simple f(x) style plots,
since the two functions can describe the x and y values to be computed
separately.  In fact, plots of the type t,f(t) are equivalent to those
produced with f(x) because the x values are computed using the identity
function.  Similarly, 3-d plots of the type u,v,f(u,v) are equivalent to
f(x,y).

Note that the order the parametric functions are specified is xfunction,
yfunction (and zfunction) and that each operates over the common parametric
domain.

Also, the `set parametric` function implies a new range of values.  Whereas
the normal f(x) and f(x,y) style plotting assume an xrange and yrange (and
zrange), the parametric mode additionally specifies a trange, urange, and
vrange.  These ranges may be set directly with @ref{trange}, @ref{urange},
and @ref{vrange}, or by specifying the range on the `plot` or `splot`
commands.  Currently the default range for these parametric variables is
[-5:5].  Setting the ranges to something more meaningful is expected.

@node plot_, pm3d, parametric_, set-show
@subsection plot

@c ?commands show plot
@c ?show plot
The `show plot` command shows the current plotting command as it results
from the last `plot` and/or `splot` and possible subsequent @ref{replot} commands.

In addition, the `show plot add2history` command adds this current plot
command into the `history`. It is useful if you have used @ref{replot} to add
more curves to the current plot and you want to edit the whole command now.

@node pm3d, palette, plot_, set-show
@subsection pm3d

@c ?commands set pm3d
@c ?commands show pm3d
@c ?set pm3d
@c ?show pm3d
@cindex pm3d
@opindex pm3d


pm3d is an `splot` style for drawing palette-mapped 3d and 4d data as
color/gray maps and surfaces.  It uses a pm3d algorithm which allows plotting
gridded as well as non-gridded data without preprocessing, even when the data
scans do not have the same number of points.

Drawing of color surfaces is available on terminals supporting filled colored
polygons with color mapping specified by @ref{palette}. Currently supported
terminals include

@example
  Screen terminals:
    OS/2 Presentation Manager
    X11
    Linux VGA (vgagl)
    GGI
    Windows
    AquaTerm (Mac OS X)
    wxWidgets (wxt)
  Files:
    PostScript
    pslatex, pstex, epslatex
    gif, png, jpeg
    (x)fig
    tgif
    cgm
    pdf
    svg
    emf

@end example

Let us first describe how a map/surface is drawn.  The input data come from an
evaluated function or from an @ref{file}.  Each surface consists of a
sequence of separate scans (isolines).  The pm3d algorithm fills the region
between two neighbouring points in one scan with another two points in the
next scan by a gray (or color) according to z-values (or according to an
additional 'color' column, see help for @ref{using}) of these 4 corners; by default
the 4 corner values are averaged, but this can be changed by the option
`corners2color`.  In order to get a reasonable surface, the neighbouring scans
should not cross and the number of points in the neighbouring scans should not
differ too much; of course, the best plot is with scans having same number of
points.  There are no other requirements (e.g. the data need not be gridded).
Another advantage is that the pm3d algorithm does not draw anything outside of
the input (measured or calculated) region.

Surface coloring works with the following input data:

1. splot of function or of data file with one or three data columns: The
gray/color scale is obtained by mapping the averaged (or `corners2color`)
z-coordinate of the four corners of the above-specified quadrangle into the
range [min_color_z,max_color_z] of @ref{zrange} or @ref{cbrange} providing a gray value
in the range [0:1].  This value can be used directly as the gray for gray maps.
The normalized gray value can be further mapped into a color---see @ref{palette}
for the complete description.

2. splot of data file with two or four data columns: The gray/color value is
obtained by using the last-column coordinate instead of the z-value, thus
allowing the color and the z-coordinate be mutually independent.  This can be
used for 4d data drawing.

Other notes:

1. The term 'scan' referenced above is used more among physicists than the
term 'iso_curve' referenced in gnuplot documentation and sources.  You measure
maps recorded one scan after another scan, that's why.

2. The 'gray' or 'color' scale is a linear mapping of a continuous variable
onto a smoothly varying palette of colors. The mapping is shown in a
rectangle next to the main plot. This documentation refers to this as a
"colorbox", and refers to the indexing variable as lying on the colorbox axis.
See `set colorbox`, @ref{cbrange}.

3. To use pm3d coloring to generate a two-dimensional plot rather than a 3D
surface, use `set view map` or `set pm3d map`.

Syntax (the options can be given in any order):
@example
      set pm3d @{
                 @{ at <bst combination> @}
                 @{ interpolate <steps in scan>,<steps between scans> @}
                 @{ scansautomatic | scansforward | scansbackward | depthorder @}
                 @{ flush @{ begin | center | end @} @}
                 @{ ftriangles | noftriangles @}
                 @{ clip1in | clip4in @}
                 @{ corners2color @{ mean|geomean|median|min|max|c1|c2|c3|c4 @} @}
                 @{ hidden3d <linestyle> | nohidden3d @}
                 @{ implicit | explicit @}
                 @{ map @}
               @}
      show pm3d
      unset pm3d

@end example

Color surface is drawn if data or function @ref{style} is set to pm3d globally or
via 'with' option, or if the option `implicit` is on---then the pm3d surface
is combined with the line surface mesh. See bottom of this section for mode
details.

Color surface can be drawn at the base or top (then it is a gray/color planar
map) or at z-coordinates of surface points (gray/color surface).  This is
defined by the `at` option with a string of up to 6 combinations of `b`, `t`
and `s`. For instance, `at b` plots at bottom only, `at st` plots firstly
surface and then top map, while `at bstbst` will never by seriously used.

Colored quadrangles are plotted one after another.  When plotting surfaces
(`at s`), the later quadrangles overlap (overdraw) the previous ones.
(Gnuplot is not virtual reality tool to calculate intersections of filled
polygon meshes.)  You may try to switch between `scansforward` and
`scansbackward` to force the first scan of the data to be plotted first or
last.  The default is `scansautomatic` where gnuplot makes a guess about scans
order.  On the other hand, the @ref{depthorder} option completely reorders the
qudrangles. The rendering is performed after a depth sorting, which allows to
visualize even complicated surfaces; see @ref{depthorder} for more
details.

If two subsequent scans do not have same number of points, then it has to be
decided whether to start taking points for quadrangles from the beginning of
both scans (`flush begin`), from their ends (`flush end`) or to center them
(`flush center`).  Note, that `flush (center|end)` are incompatible with
`scansautomatic`: if you specify `flush center` or `flush end` and
`scansautomatic` is set, it is silently switched to `scansforward`.

If two subsequent scans do not have the same number of points, the option
`ftriangles` specifies whether color triangles are drawn at the scan tail(s)
where there are not enough points in either of the scan. This can be used to
draw a smooth map boundary.

Clipping with respect to x, y coordinates of quadrangles can be done in two
ways.  `clip1in`: all 4 points of each quadrangle must be defined and at least
1 point of the quadrangle must lie in the x and y ranges.  `clip4in`: all 4
points of each quadrangle must lie in the x and y ranges.

There is a single gray/color value associated to each drawn pm3d quadrangle
(no smooth color change among vertices).  The value is calculated from
z-coordinates from the surrounding corners according to `corners2color
<option>`.  The options 'mean' (default), 'geomean' and 'median' produce
various kinds of surface color smoothing, while options 'min' and 'max' choose
minimal or maximal value, respectively. This may not be desired for pixel
images or for maps with sharp and intense peaks, in which case the options
'c1', 'c2', 'c3' or 'c4' can be used instead to assign the quadrangle color
based on the z-coordinate of only one corner.  Some experimentation may be
needed to determine which corner corresponds to 'c1', as the orientation
depends on the drawing direction.  Because the pm3d algorithm does not extend
the colored surface outside the range of the input data points, the 'c<j>'
coloring options will result in pixels along two edges of the grid not
contributing to the color of any quadrangle.  For example, applying the pm3d
algorithm to the 4x4 grid of data points in script `demo/pm3d.dem` (please have
a look) produces only (4-1)x(4-1)=9 colored rectangles.

Another drawing algorithm, which would draw quadrangles around a given node
by taking corners from averaged (x,y)-coordinates of its surrounding 4 nodes
while using node's color, could be implemented in the future. This is already
done for drawing images (2D grids) via `image` and `rgbimage` styles.

Notice that ranges of z-values and color-values for surfaces are adjustable
independently by @ref{zrange}, @ref{cbrange}, as well as `set log` for z or
cb.  Maps can be adjusted by the cb-axis only; see also `set view map` and
`set colorbox`.

The option @ref{hidden3d} takes as the argument a linestyle which must be created
by `set style line ...`. (The style need not to be present when setting pm3d,
but it must be present when plotting).  If set, lines are drawn using the
specified line style, taking into account hidden line removal.  This is by
far more efficient than using the command @ref{hidden3d} as it doesn't really
calculate hidden line removal, but just draws the filled polygons in the
correct order. So the recommended choice when using pm3d is
@example
      set pm3d at s hidden3d 100
      set style line 100 lt 5 lw 0.5
      unset hidden3d
      unset surf
      splot x*x+y*y

@end example

There used to be an option @{transparent|solid@} to this command.  Now
you get the same effect from `set grid @{front|layerdefault@}`,
respectively.

The `set pm3d map` is an abbreviation for `set pm3d at b`; `set view map`;
@ref{pm3d}; @ref{pm3d};.
It is used for backwards compatibility, when `set view map` was not available.
Take care that you properly use @ref{zrange} and @ref{cbrange} for input data point
filtering and color range scaling, respectively; and also `set (no)surface`
seems to have a (side?) effect.

The option `interpolate` will interpolate grid points into a finer mesh, and
color each quadrangle appropriately. For data files, this will smoothen the
color surface, and enhance spikes in a color surface. For functions,
interpolation makes little sense, except to trade off precision for memory.
It would usually make more sense to use @ref{samples} and @ref{isosamples} when working
with functions.

The coloring setup as well as the color box drawing are determined by
@ref{palette}.  There can be only one palette for the current plot.  Drawing
of several surfaces with different palettes can be achieved by @ref{multiplot}
with fixed @ref{origin} and @ref{size}; don't forget to use `set palette maxcolors`
when your terminal is running out of available colors.

On gnuplot start-up, mode is `explicit`. For historical and thus compatibility
reasons, commands `set pm3d;` (i.e. no options) and `set pm3d at X ...` (i.e.
`at` is the first option) sets mode `implicit`. Further, `set pm3d;` sets up
the other options to their default.

If the option `implicit` is on, all surface plots will be plotted additionally
to the default type, e.g.
@example
      splot 'fred.dat' with lines, 'lola.dat' with lines
@end example

would give both plots (meshes) additionally to a pm3d surface. That's what you
are used to after `set pm3d;`.

If the option `explicit` is on (or `implicit` is off) only plots specified
by the @ref{pm3d} attribute are plotted with a pm3d surface, e.g.:
@example
      splot 'fred.dat' with lines, 'lola.dat' with pm3d
@end example

would plot 'fred.dat' with lines (and only lines) and 'lola.dat' with
a pm3d surface.

If you set the default data or function style to @ref{pm3d}, e.g.:
@example
      set style data pm3d
@end example

then the options `implicit` and `explicit` have no effect.

Note that when plotting several plots, they are plotted in the order given
on the command line. This can be of interest especially for filled surfaces
which can overwrite and therefore hide part of earlier plots.

If @ref{pm3d} is specified in the `splot` command line, then it accepts the
'at' option.  The following plots draw three color surfaces at different
altitudes:
@example
      set border 4095
      set pm3d at s
      splot 10*x with pm3d at b, x*x-y*y, x*x+y*y with pm3d at t

@end example

See also help for @ref{palette}, @ref{cbrange}, `set colorbox`, @ref{pm3d}
and definitely the demo file `demo/pm3d.dem`.

@menu
* depthorder::                  
@end menu

@node depthorder,  , pm3d, pm3d
@subsubsection depthorder

@c ?commands set pm3d depthorder
@c ?set pm3d depthorder
@c ?pm3d depthorder
@cindex depthorder

By default the quadrangles making up a pm3d solid surface are rendered in the
order they are encountered along the surface grid points.  This order may be
controlled by the options `scansautomatic`|`scansforward`|`scansbackward`.
These scan options are not in general compatible with hidden-surface removal.

Gnuplot does not do true hidden surface removal for solid surfaces, but often
it is sufficient to render the component quadrangles in order from furthest
to closest.  This mode may be selected using the options
@example
      set pm3d depthorder hidden3d
@end example

The @ref{depthorder} option orders the solid quadrangles; the @ref{hidden3d} option
similarly orders the bounding lines (if drawn).  Note that the global option
@ref{hidden3d} does not affect pm3d surfaces.

@node palette, pointsize, pm3d, set-show
@subsection palette

@c ?commands set palette
@c ?commands show palette
@c ?set palette
@c ?show palette
@cindex palette
@opindex palette


Palette is a color storage for use by @ref{pm3d}, filled color contours or
polygons, color histograms, color gradient background, and whatever it is
or it will be implemented...  Here it stands for a palette of smooth
"continuous" colors or grays, but let's call it just a palette.

Color palettes require terminal entries for filled color polygons and
palettes of smooth colors, are currently available for terminals listed in
help for @ref{pm3d}. The range of color values are adjustable independently by
@ref{cbrange} and `set log cb`. The whole color palette is
visualized in the `colorbox`.

Syntax:
@example
      set palette
      set palette @{
                 @{ gray | color @}
                 @{ gamma <gamma> @}
                 @{   rgbformulae <r>,<g>,<b>
                   | defined @{ ( <gray1> <color1> @{, <grayN> <colorN>@}... ) @}
                   | file '<filename>' @{datafile-modifiers@}
                   | functions <R>,<G>,<B>
                 @}
                 @{ model @{ RGB | HSV | CMY | YIQ | XYZ @} @}
                 @{ positive | negative @}
                 @{ nops_allcF | ps_allcF @}
                 @{ maxcolors <maxcolors> @}
               @}
      show palette
      show palette palette <n> @{@{float | int@}@}
      show palette gradient
      show palette fit2rgbformulae
      show palette rgbformulae
      show palette colornames

@end example

@ref{palette} (i.e. without options) sets up the default values.
Otherwise, the options can be given in any order.
@ref{palette} shows the current palette properties.

`show palette gradient` displays the gradient defining the palette (if
appropriate).  @ref{rgbformulae} prints the available fixed gray -->
color transformation formulae.  @ref{colornames} prints the
implemented color names.

`show palette palette <n>` prints to screen or to the file given by
@ref{output} table of RGB triplets calculated for the current palette settings
and a palette having <n> discrete colors.  The default wide table can be
limited to 3 columns of r,g,b float values [0..1] or integer values [0..255]
by options float or int, respectively.  This way, the current gnuplot color
palette can be loaded into other imaging applications, for example Octave.
Additionally to this textual list of RGB table, you can enjoy command @ref{palette} to draw graphically the R,G,B profiles for the current palette.

The following options determine the coloring properties.

Figure using this palette can be `gray` or `color`.  For instance, in @ref{pm3d}
color surfaces the gray of each small spot is obtained by mapping the averaged
z-coordinate of the 4 corners of surface quadrangles into the range
[min_z,max_z] providing range of grays [0:1]. This value can be used directly
as the gray for gray maps. The color map requires a transformation gray -->
(R,G,B), i.e. a mapping [0:1] --> ([0:1],[0:1],[0:1]).

Basically two different types of mappings can be used:  Analytic formulae to
convert gray to color, or discrete mapping tables which are interpolated.
@ref{rgbformulae} and @ref{functions} use analytic formulae whereas
@ref{defined} and @ref{file} use interpolated tables.  @ref{rgbformulae} reduces the size of postscript output to a minimum.

The command `show palette fit2rgbformulae` finds the best matching @ref{rgbformulae} for the current @ref{palette}. Naturally, it makes sense
to use it for non-rgbformulae palettes. This command can be found useful
mainly for external programs using the same rgbformulae definition of palettes
as gnuplot, like zimg (
@uref{http://zimg.sourceforge.net,http://zimg.sourceforge.net
}
@example
 ).

@end example

`set palette gray` switches to a gray only palette. @ref{rgbformulae},
@ref{defined}, @ref{file} and @ref{functions} switch
to a color mapping. `set palette color` is an easy way to switch back from the
gray palette to the last color mapping.

Automatic gamma correction via `set palette gamma <gamma>` can be done for
gray maps only (`set palette gray`).  Linear mapping to gray is for gamma
equals 1, see @ref{palette}.  Gamma is ignored for color mappings.

Most terminals support only discrete number of colors (e.g. 256 colors in
gif).  All entries of the palette remaining after the default gnuplot linetype
colors declaration are allocated for pm3d by default.  Then @ref{multiplot} could
fail if there are no more color positions in the terminal available.  Then you
should use `set palette maxcolors <maxcolors>` with a reasonably small value.
This option can also be used to separate levels of z=constant in discrete
steps, thus to emulate filled contours. Default value of 0 stays for
allocating all remaining entries in the terminal palette or for to use exact
mapping to RGB.

RGB color space might not be the most useful color space to work in.  For that
reason you may change the color space with `model` to one of `RGB`, `HSV`,
`CMY`, `YIQ` and `XYZ`.  Using color names for @ref{defined} tables
and a color space other than RGB will result in funny colors.  All explanation
have been written for RGB color space, so please note, that `R` can be `H`,
`C`, `Y`, or `X`, depending on the actual color space (`G` and `B`
accordingly).

All values for all color spaces are limited to [0,1].

RGB stands for Red, Green and Blue;  CMY stands for Cyan, Magenta and Yellow;
HSV stands for Hue, Saturation, and Value;  YIQ is the color model used by
the U.S. Commercial Color Television Broadcasting, it is basically an RGB
recoding with downward compatibility for black and white television;
XYZ are the three primary colors of the color model defined by the 'Commission
Internationale de l'Eclairage' (CIE).
For more information on color models see:
@uref{http://www.cs.rit.edu/~ncs/color/glossary.htm,http://www.cs.rit.edu/~ncs/color/glossary.htm
}
and
@uref{http://cs.fit.edu/wds/classes/cse5255/cse5255/davis/index.html,http://cs.fit.edu/wds/classes/cse5255/cse5255/davis/index.html
}


@menu
* rgbformulae::                 
* defined_::                    
* functions_::                  
* file::                        
* gamma_correction::            
* postscript::                  
* colornames::                  
@end menu

@node rgbformulae, defined_, palette, palette
@subsubsection rgbformulae

@c ?commands set palette rgbformulae
@c ?set palette rgbformulae
@c ?palette rgbformulae
@cindex rgbformulae

@cindex colors

For @ref{rgbformulae} three suitable mapping functions have
to be chosen.  This is done via `rgbformulae <r>,<g>,<b>`.  The available
mapping functions are listed by @ref{rgbformulae}.  Default is
`7,5,15`, some other examples are `3,11,6`, `21,23,3` or `3,23,21`.  Negative
numbers, like `3,-11,-6`, mean inverted color (i.e.  1-gray passed into the
formula, see also `positive` and `negative` options below).

Some nice schemes in RGB color space
@example
   7,5,15   ... traditional pm3d (black-blue-red-yellow)
   3,11,6   ... green-red-violet
   23,28,3  ... ocean (green-blue-white); try also all other permutations
   21,22,23 ... hot (black-red-yellow-white)
   30,31,32 ... color printable on gray (black-blue-violet-yellow-white)
   33,13,10 ... rainbow (blue-green-yellow-red)
   34,35,36 ... AFM hot (black-red-yellow-white)

@end example

A full color palette in HSV color space
@example
   3,2,2    ... red-yellow-green-cyan-blue-magenta-red

@end example

Please note that even if called @ref{rgbformulae} the formulas might actually
determine the <H>,<S>,<V> or <X>,<Y>,<Z> or ... color components as usual.

Use `positive` and `negative` to invert the figure colors.
@c ^ <a name="positive"></a>
@c ^ <a name="negative"></a>

Note that it is possible to find a set of the best matching rgbformulae for any
other color scheme by the command
@example
   show palette fit2rgbformulae

@end example

@node defined_, functions_, rgbformulae, palette
@subsubsection defined

@c ?commands set palette defined
@c ?set palette defined
@c ?palette defined
@cindex colors

Gray-to-rgb mapping can be manually set by use of @ref{defined}:  A color gradient
is defined and used to give the rgb values.  Such a  gradient is a piecewise
linear mapping from gray values in [0,1] to the RGB space [0,1]x[0,1]x[0,1].
You have to specify the gray values and the corresponding RGB values in
between a linear interpolation shall take place:

Syntax:
@example
      set palette  defined @{ ( <gray1> <color1> @{, <grayN> <colorN>@}... ) @}

@end example

<grayX> are gray values which are mapped to [0,1] and <colorX> are the
corresponding rgb colors.  The color can be specified in three different
ways:

@example
     <color> :=  @{ <r> <g> <b> | '<color-name>' | '#rrggbb' @}

@end example

Either by three numbers (each in [0,1]) for red, green and blue, separated by
whitespace, or the name of the color in quotes or X style color specifiers
also in quotes.  You may freely mix the three types in a gradient definition,
but the named color "red" will be something strange if RGB is not selected
as color space.  Use @ref{colornames} for a list of known color
names.

Please note, that even if written as <r>, this might actually be the
<H> component in HSV color space or <X> in CIE-XYZ space, or ...
depending on the selected color model.

The <gray> values have to form an ascending sequence of real numbers; the
sequence will be automatically rescaled to [0,1].

@ref{defined} (without a gradient definition in braces) switches to
RGB color space and uses a preset full-spectrum color gradient.
Use `show palette gradient` to display the gradient.

Examples:

To produce a gray palette (useless but instructive) use:
@example
      set palette model RGB
      set palette defined ( 0 "black", 1 "white" )

@end example

To produce a blue yellow red palette use (all equivalent):
@example
      set palette defined ( 0 "blue", 1 "yellow", 2 "red" )
      set palette defined ( 0 0 0 1, 1 1 1 0, 2 1 0 0 )
      set palette defined ( 0 "#0000ff", 1 "#ffff00", 2 "#ff0000" )

@end example

To produce some rainbow-like palette use:
@example
      set palette defined ( 0 "blue", 3 "green", 6 "yellow", 10 "red" )

@end example

Full color spectrum within HSV color space:
@example
      set palette model HSV
      set palette defined ( 0 0 1 1, 1 1 1 1 )
      set palette defined ( 0 0 1 0, 1 0 1 1, 6 0.8333 1 1, 7 0.8333 0 1)

@end example

To produce a palette with few colors only use:
@example
      set palette model RGB maxcolors 4
      set palette defined ( 0 "blue", 1 "green", 2 "yellow", 3 "red" )

@end example

'Traffic light' palette (non-smooth color jumps at gray = 1/3 and 2/3).
@example
      set palette model RGB
      set palette defined (0 "dark-green", 1 "green", 1 "yellow", \
                           2 "dark-yellow", 2 "red", 3 "dark-red" )

@end example


@node functions_, file, defined_, palette
@subsubsection functions

@c ?commands set palette functions
@c ?set palette functions
@c ?palette functions
Use `set palette functions <Rexpr>, <Gexpr>, <Bexpr>` to define three formulae
for the R(gray), G(gray) and B(gray) mapping.  The three formulae may depend
on the variable `gray` which will take values in [0,1] and should also
produce values in [0,1].
Please note that <Rexpr> might be a formula for the H-value if HSV color
space has been chosen (same for all other formulae and color spaces).

Examples:

To produce a full color palette use:
@example
      set palette model HSV functions gray, 1, 1

@end example

A nice black to gold palette:
@example
      set palette model XYZ functions gray**0.35, gray**0.5, gray**0.8

@end example

A gamma-corrected black and white palette
@example
      gamma = 2.2
      color(gray) = gray**(1./gamma)
      set palette model RGB functions color(gray), color(gray), color(gray)

@end example


@node file, gamma_correction, functions_, palette
@subsubsection file

@c ?commands set palette file
@c ?set palette file
@c ?palette file
@ref{file} is basically a `set palette defined (<gradient>)` where
<gradient> is read from a datafile.  Either 4 columns (gray,R,G,B) or
just three columns (R,G,B) have to be selected via the @ref{using} data file
modifier.  In the three column case, the line number will be used as gray.
The gray range is automatically rescaled to [0,1].  The file is read as a
normal data file, so all datafile modifiers can be used.
Please note, that `R` might actually be e.g. `H` if HSV color space is
selected.

As usual <filename> may be `'-'` which means that the data follow the command
inline and are terminated by a single `e` on a line of its own.

Use `show palette gradient` to display the gradient.

Examples:

Read in a palette of RGB triples each in range [0,255]:
@example
      set palette file 'some-palette' using ($1/255):($2/255):($3/255)

@end example

Equidistant rainbow (blue-green-yellow-red) palette:
@example
      set palette model RGB file "-"
      0 0 1
      0 1 0
      1 1 0
      1 0 0
      e

@end example

Binary palette files are supported as well, see `binary general`. Example:
put 64 triplets of R,G,B doubles into file palette.bin and load it by
@example
      set palette file "palette.bin" binary record=64 using 1:2:3

@end example



@node gamma_correction, postscript, file, palette
@subsubsection gamma correction

@c ?commands set palette gamma-correction
@c ?set palette gamma-correction
@c ?palette gamma-correction
@cindex gamma-correction

For gray mappings gamma correction can be turned on by `set palette gamma
<gamma>`.  <gamma> defaults to 1.5 which is quite suitable for most
terminals.

For color mappings no automatic gamma correction is done by gnuplot.  However,
you may easily implement gamma correction.  Here is an example for a gray
scale image by use of explicit functions for the red, green and blue component
with slightly different values of gamma

Example:
@example
      set palette model RGB
      set palette functions gray**0.64, gray**0.67, gray**0.70

@end example

To use gamma correction with interpolated gradients specify intermediate
gray values with appropriate colors.  Instead of

@example
      set palette defined ( 0 0 0 0, 1 1 1 1 )

@end example

use e.g.

@example
      set palette defined ( 0 0 0 0, 0.5 .73 .73 .73, 1 1 1 1 )

@end example

or even more intermediate points until the linear interpolation fits the
"gamma corrected" interpolation well enough.


@node postscript, colornames, gamma_correction, palette
@subsubsection postscript

@c ?commands set palette postscript
@c ?set palette postscript
In order to reduce the size of postscript files, the gray value and not all
three calculated r,g,b values are written to the file.  Therefore the
analytical formulae are coded directly in the postscript language as a header
just before the pm3d drawing, see /g and /cF definitions.  Usually, it makes
sense to write therein definitions of only the 3 formulae used.  But for
multiplot or any other reason you may want to manually edit the
transformations directly in the postscript file.  This is the default option
`nops_allcF`.  Using the option `ps_allcF` writes postscript definitions of
all formulae.  This you may find interesting if you want to edit the
postscript file in order to have different palettes for different surfaces
in one graph.  Well, you can achieve this functionality by @ref{multiplot} with
fixed @ref{origin} and @ref{size}.

If pm3d map has been plotted from gridded or almost regular data with an
output to a postscript file, then it is possible to reduce the size of this
postscript file up to at about 50% by the enclosed awk script
`pm3dCompress.awk`.  This you may find  interesting if you intend to keep the
file for including it into your publication or before downloading a very large
file into a slow printer. Usage:
@example
    awk -f pm3dCompress.awk thefile.ps >smallerfile.ps

@end example

If pm3d map has been plotted from rectangular gridded data with an output
to a postscript file, then it is possible to reduce the file size even more
by the enclosed awk script `pm3dConvertToImage.awk`.  Usage:
@example
    awk -f pm3dConvertToImage.awk <thefile.ps >smallerfile.ps

@end example

You may manually change the postscript output from gray to color and vice
versa and change the definition of <maxcolors>.

@node colornames,  , postscript, palette
@subsubsection colornames

@cindex colornames

@c ?show palette colornames
@c ?show colornames
Gnuplot knows a limited number of color names. You can use these to define
the color range spanned by a pm3d palette, or to assign a terminal-independent
color to a particular linetype or linestyle. To see the list of known color
names, use the command @ref{colornames}.
See @ref{palette}, `linestyle`.

@node pointsize, polar, palette, set-show
@subsection pointsize

@c ?commands set pointsize
@c ?commands show pointsize
@c ?set pointsize
@c ?show pointsize
@cindex pointsize
@opindex pointsize


The @ref{pointsize} command scales the size of the points used in plots.

Syntax:
@example
      set pointsize <multiplier>
      show pointsize

@end example

The default is a multiplier of 1.0.  Larger pointsizes may be useful to
make points more visible in bitmapped graphics.

The pointsize of a single plot may be changed on the `plot` command.
See @ref{with} for details.

Please note that the pointsize setting is not supported by all terminal
types.

@node polar, print_, pointsize, set-show
@subsection polar

@c ?commands set polar
@c ?commands unset polar
@c ?commands show polar
@c ?set polar
@c ?unset polar
@c ?show polar
@cindex polar
@opindex polar


@cindex nopolar

The `set polar` command changes the meaning of the plot from rectangular
coordinates to polar coordinates.

Syntax:
@example
      set polar
      unset polar
      show polar

@end example

There have been changes made to polar mode in version 3.7, so that scripts
for `gnuplot` versions 3.5 and earlier will require modification.  The main
change is that the dummy variable t is used for the angle so that the x and
y ranges can be controlled independently.  Other changes are:
1) tics are no longer put along the zero axes automatically
---use `set xtics axis nomirror`; `set ytics axis nomirror`;
2) the grid, if selected, is not automatically polar
---use `set grid polar`;
3) the grid is not labelled with angles
---use @ref{label} as necessary.

In polar coordinates, the dummy variable (t) is an angle.  The default range
of t is [0:2*pi], or, if degree units have been selected, to [0:360] (see
@ref{angles}).

The command `unset polar` changes the meaning of the plot back to the default
rectangular coordinate system.

The `set polar` command is not supported for `splot`s.  See the @ref{mapping}
command for similar functionality for `splot`s.

While in polar coordinates the meaning of an expression in t is really
r = f(t), where t is an angle of rotation.  The trange controls the domain
(the angle) of the function, and the x and y ranges control the range of the
graph in the x and y directions.  Each of these ranges, as well as the
rrange, may be autoscaled or set explicitly.  See @ref{xrange} for details
of all the @ref{ranges} commands.

Example:
@example
      set polar
      plot t*sin(t)
      plot [-2*pi:2*pi] [-3:3] [-3:3] t*sin(t)

@end example

The first `plot` uses the default polar angular domain of 0 to 2*pi.  The
radius and the size of the graph are scaled automatically.  The second `plot`
expands the domain, and restricts the size of the graph to [-3:3] in both
directions.

You may want to `set size square` to have `gnuplot` try to make the aspect
ratio equal to unity, so that circles look circular.
See also
@uref{http://www.gnuplot.info/demo/polar.html,polar demos (polar.dem)
}
and
@uref{http://www.gnuplot.info/demo/poldat.html,polar data plot (poldat.dem).
}

@node print_, object, polar, set-show
@subsection print

@c ?commands set print
@c ?commands show print
@c ?set print
@c ?show print
The @ref{print} command redirects the output of the @ref{print} command to a file.

Syntax:
@example
      set print
      set print "-"
      set print "<filename>"
      set print "<filename>" append
      set print "|<shell_command>"

@end example

Without "<filename>", the output file is restored to <STDERR>.  The <filename>
"-" means <STDOUT>. The `append` flag causes the file to be opened in append
mode.  A <filename> starting with "|" is opened as a pipe to the
<shell_command> on platforms that support piping.

@node object, rmargin, print_, set-show
@subsection object

@cindex object
@opindex object


@cindex rectangle

@c ?commands set object
@c ?commands show object
@c ?commands set object rectangle
@c ?commands show object rectangle
@c ?set object
@c ?show object
@c ?set object rectangle
@c ?show object rectangle
This command defines a single object, which will appear in all subsequent
2D plots. You may define as many objects as you like. Currently the only
object type supported is `rectangle`.
Each rectangle is specified by a pair of points that define diagonal vertices.
A default set of style properties (fill, color, border) are inherited from
those set by the command `set style rectangle`, but each rectangle can also be
given individual style properties.

Syntax:
@example
    set object <index> rectangle
        @{from <position> @{to|rto@} <position> |
         center <position> size <w>,<h> |
         at <position> size <w>,<h>@}
        @{front|back|behind@} @{fc|fillcolor <colorspec>@} @{fs <fillstyle>@}
        @{default@} @{lw|linewidth <width>@}

@end example

The position of the rectangle may be specified by giving the position of two
diagonal corners (bottom left and top right) or by giving the position of the
center followed by the width and the height.  In either case the positions
may be given in axis, graph, or screen coordinates. See `coordinates`.
The options `at` and `center` are synonyms.

Setting `front` will draw the rectangle in front of all plot elements, but
behind any labels that are also marked `front`. Setting `back` will place the
rectangle behind all plot curves and labels. Setting `behind` will place the
rectangle behind everything including the axes and `back` rectangles, and can
be used to provide a colored background for the entire graph or page.

The fill color of the rectangle is taken from the <colorspec>. `fillcolor`
may be abbreviated `fc`.  The fill style is taken from <fillstyle>.
See @ref{colorspec} and `fillstyle`.  If the keyword `default` is given,
these properties are inherited from the default settings of at the time a plot
is drawn. See `set style rectangle`.

Examples:
@example
    # Force the entire area enclosed by the axes to have background color cyan
    set object 1 rect from graph 0, graph 0 to graph 1, graph 1 back
    set object 1 rect fc rgb "cyan" fillstyle solid 1.0

@end example

@example
    # Position a red square with lower left at 0,0 and upper right at 2,3
    set object 2 rect from 0,0 to 2,3 fc lt 1

@end example

@example
    # Position an empty rectangle (no fill) with a blue border
    set object 3 rect from 0,0 to 2,3 fs empty border 3

@end example

@example
    # Return fill and color to the default style but leave vertices unchanged
    set object 2 rect default

@end example


@node rmargin, rrange, object, set-show
@subsection rmargin

@c ?commands set rmargin
@c ?set rmargin
@cindex rmargin
@opindex rmargin


The command @ref{rmargin} sets the size of the right margin.
Please see @ref{margin} for details.

@node rrange, samples, rmargin, set-show
@subsection rrange

@c ?commands set rrange
@c ?commands show rrange
@c ?set rrange
@c ?show rrange
@cindex rrange
@opindex rrange


The @ref{rrange} command sets the range of the radial coordinate for a
graph in polar mode.  Please see @ref{xrange} for details.

@node samples, size, rrange, set-show
@subsection samples

@c ?commands set samples
@c ?commands show samples
@c ?set samples
@c ?show samples
@cindex samples
@opindex samples


The sampling rate of functions, or for interpolating data, may be changed
by the @ref{samples} command.

Syntax:
@example
      set samples <samples_1> @{,<samples_2>@}
      show samples

@end example

By default, sampling is set to 100 points.  A higher sampling rate will
produce more accurate plots, but will take longer.  This parameter has no
effect on data file plotting unless one of the interpolation/approximation
options is used.  See @ref{smooth} re 2-d data and @ref{cntrparam} and
@ref{dgrid3d} re 3-d data.

When a 2-d graph is being done, only the value of <samples_1> is relevant.

When a surface plot is being done without the removal of hidden lines, the
value of samples specifies the number of samples that are to be evaluated for
the isolines.  Each iso-v line will have <sample_1> samples and each iso-u
line will have <sample_2> samples.  If you only specify <samples_1>,
<samples_2> will be set to the same value as <samples_1>.  See also
@ref{isosamples}.

@node size, style, samples, set-show
@subsection size

@c ?commands set size
@c ?commands show size
@c ?set size
@c ?show size
@cindex size
@opindex size


@c ?aspect ratio
Syntax:
@example
      set size @{@{no@}square | ratio <r> | noratio@} @{<xscale>,<yscale>@}
      show size

@end example

The <xscale> and <yscale> values are scale factors for the size of the plot,
which includes the graph, labels, and margins.

Important note:
@example
      In earlier versions of gnuplot, some terminal types used the values from
      @ref{size} to control also the size of the output canvas; others did not.
      In version 4.2 almost all terminals now follow the following convention:

@end example

`set term <terminal_type> size <XX>, <YY>` controls the size of the output
file, or `canvas`. Please see individual terminal documentation for allowed
values of the size parameters.  By default, the plot will fill this canvas.

`set size <XX>, <YY>` scales the plot itself relative to the size of the
canvas.  Scale values less than 1 will cause the plot to not fill the entire
canvas.  Scale values larger than 1 will cause only a portion of the plot to
fit on the canvas.  Please be aware that setting scale values larger than 1
may cause problems on some terminal types.

`ratio` causes `gnuplot` to try to create a graph with an aspect ratio of <r>
(the ratio of the y-axis length to the x-axis length) within the portion of
the plot specified by <xscale> and <yscale>.

The meaning of a negative value for <r> is different.  If <r>=-1, gnuplot
tries to set the scales so that the unit has the same length on both the x
and y axes (suitable for geographical data, for instance).  If <r>=-2, the
unit on y has twice the length of the unit on x, and so on.

The success of `gnuplot` in producing the requested aspect ratio depends on
the terminal selected.  The graph area will be the largest rectangle of
aspect ratio <r> that will fit into the specified portion of the output
(leaving adequate margins, of course).

`square` is a synonym for `ratio 1`.

Both `noratio` and `nosquare` return the graph to the default aspect ratio
of the terminal, but do not return <xscale> or <yscale> to their default
values (1.0).

`ratio` and `square` have no effect on 3-d plots, but do affect 3D projections
created using `set view map`.  Similarly `set view equal` forces the
x and y axes of a 3D onto the same scale.

Examples:

To set the size so that the plot fills the available canvas:
@example
      set size 1,1

@end example

To make the graph half size and square use:
@example
      set size square 0.5,0.5

@end example

To make the graph twice as high as wide use:
@example
      set size ratio 2

@end example

See also
@uref{http://www.gnuplot.info/demo/airfoil.html,airfoil demo.
}

@node style, surface, size, set-show
@subsection style

@c ?set style
@c ?show style
@c ?unset style
@c ^ <a name="set style <style>"></a>
Default plotting styles are chosen with the `set style data` and
`set style function` commands.  See @ref{with} for information about how to
override the default plotting style for individual functions and data sets.
See `plotting styles` for a complete list of styles.

Syntax:
@example
      set style function <style>
      set style data <style>
      show style function
      show style data

@end example

Default styles for specific plotting elements may also be set.

Syntax:
@example
      set style arrow <n> <arrowstyle>
      set style fill <fillstyle>
      set style histogram <histogram style options>
      set style line <n> <linestyle>

@end example


@menu
* set_style_arrow::             
* set_style_data::              
* set_style_fill::              
* set_style_function::          
* set_style_increment::         
* set_style_line::              
* plotting_styles::             
* set_style_rectangle::         
@end menu

@node set_style_arrow, set_style_data, style, style
@subsubsection set style arrow

@c ?commands set style arrow
@c ?commands unset style arrow
@c ?commands show style arrow
@c ?set style arrow
@c ?unset style arrow
@c ?show style arrow
@cindex arrowstyle

@c ^ <a name="arrowtype"></a>
@c ^ <a name="arrowwidth"></a>
Each terminal has a default set of arrow and point types, which can be seen
by using the command @ref{test}.  @ref{arrow} defines a set of arrow types
and widths and point types and sizes so that you can refer to them later by
an index instead of repeating all the information at each invocation.

Syntax:
@example
      set style arrow <index> default
      set style arrow <index> @{nohead | head | heads@}
                              @{size <length>,<angle>@{,<backangle>@}@}
                              @{filled | empty | nofilled@}
                              @{front | back@}
                              @{ @{linestyle | ls <line_style>@}
                                | @{linetype | lt <line_type>@}
                                  @{linewidth | lw <line_width@} @}
      unset style arrow
      show style arrow

@end example

<index> is an integer that identifies the arrowstyle.

If `default` is given all arrow style parameters are set to their default
values.

If the linestyle <index> already exists, only the given parameters are
changed while all others are preserved.  If not, all undefined values are
set to the default values.

Specifying `nohead` produces arrows drawn without a head---a line segment.
This gives you yet another way to draw a line segment on the plot.  By
default, arrows have one head. Specifying `heads` draws arrow heads on both
ends of the line.

Head size can be controlled by `size <length>,<angle>` or
`size <length>,<angle>,<backangle>`, where `<length>` defines length of each
branch of the arrow head and `<angle>` the angle (in degrees) they make with
the arrow.  `<Length>` is in x-axis units; this can be changed by `first`,
`second`, `graph`, `screen`, or `character` before the <length>;  see
`coordinates` for details.  `<Backangle>` only takes effect when `filled`
or `empty` is also used.  Then, `<backangle>` is the angle (in degrees) the
back branches make with the arrow (in the same direction as `<angle>`).
The `fig` terminal has a restricted backangle function. It supports three
different angles. There are two thresholds: Below 70 degrees, the arrow head
gets an indented back angle. Above 110 degrees, the arrow head has an acute
back angle. Between these thresholds, the back line is straight.

Specifying `filled` produces filled arrow heads (if heads are used).
Filling is supported on filled-polygon capable terminals, see help of @ref{pm3d}
for their list, otherwise the arrow heads are closed but not filled.
The same result (closed but not filled arrow head) is reached by specifying
`empty`.  Further, filling and outline is obviously not supported on
terminals drawing arrows by their own specific routines, like `metafont`,
`metapost`, `latex` or `tgif`.

The line style may be selected from a user-defined list of line styles
(see `set style line`) or may be defined here by providing values for
`<line_type>` (an index from the default list of styles) and/or
`<line_width>` (which is a  multiplier for the default width).

Note, however, that if a user-defined line style has been selected, its
properties (type and width) cannot be altered merely by issuing another
@ref{arrow} command with the appropriate index and `lt` or `lw`.

If `front` is given, the arrows are written on top of the graphed data. If
`back` is given (the default), the arrow is written underneath the graphed
data.  Using `front` will prevent a arrow from being obscured by dense data.

Examples:

To draw an arrow without an arrow head and double width, use:
@example
      set style arrow 1 nohead lw 2
      set arrow arrowstyle 1

@end example

@example
 See also @ref{arrow} for further examples.

@end example


@node set_style_data, set_style_fill, set_style_arrow, style
@subsubsection set style data

@c ?commands set style data
@c ?commands show style data
@c ?set style data
@c ?show style data
@c ?data style
The `set style data` command changes the default plotting style for data
plots.

Syntax:
@example
      set style data <plotting-style>
      show style data

@end example

See `plotting styles` for the choices.  If no choice is given, the choices are
listed.  `show style data` shows the current default data plotting style.

@node set_style_fill, set_style_function, set_style_data, style
@subsubsection set style fill

@c ?commands set style fill
@c ?commands show style fill
@c ?set style fill
@c ?show style fill
@cindex fillstyle

The `set style fill` command is used to set the style of boxes,
histograms, candlesticks and filledcurves.

Syntax:
@example
      set style fill @{empty | solid @{<density>@} | pattern @{<n>@}@}
                     @{border @{<linetype>@} | noborder@}

@end example

The default fillstyle is `empty`.

The `solid` option causes filling with a solid color, if the terminal
supports that. The <density> parameter specifies the intensity of the
fill color. At a <density> of 0.0, the box is empty, at <density> of 1.0,
the inner area is of the same color as the current linetype.
Some terminal types can vary the density continuously; others implement
only a few levels of partial fill.  If no <density> parameter is given,
it defaults to 1.

The `pattern` option causes filling to be done with a fill pattern supplied
by the terminal driver.  The kind and number of available fill patterns
depend on the terminal driver.  If multiple datasets using filled boxes are
plotted, the pattern cycles through all available pattern types, starting
from pattern <n>, much as the line type cycles for multiple line plots.

The `empty` option causes filled boxes not to be filled. This is the default.

By default, @ref{border}, the box is bounded by a solid line of the current
linetype. `border <lt>` specifies that a border is to be drawn using
linetype <lt>. `noborder` specifies that no bounding lines are drawn.

@node set_style_function, set_style_increment, set_style_fill, style
@subsubsection set style function

@c ?commands set style function
@c ?commands show style function
@c ?set style function
@c ?show style function
@c ?function style
The `set style function` command changes the default plotting style for
function plots.

Syntax:
@example
      set style function <plotting-style>
      show style function

@end example

See `plotting styles` for the choices.  If no choice is given, the choices are
listed.  `show style function` shows the current default function plotting
style.

@node set_style_increment, set_style_line, set_style_function, style
@subsubsection set style increment

@c ?commands set style increment
@c ?commands show style increment
@c ?set style increment
@c ?show style increment
Syntax:
@example
      set style increment @{default|userstyles@}
      show style increment

@end example

By default, successive plots within the same graph will use successive
linetypes from the default set for the current terminal type.
However, choosing `set style increment user` allows you to step through
the user-defined line styles rather than through the default linetypes.

Example:

@example
      set style line 1 lw 2 lc rgb "gold"
      set style line 2 lw 2 lc rgb "purple"
      set style line 4 lw 1 lc rgb "sea-green"
      set style increment user

@end example

@example
      plot f1(x), f2(x), f3(x), f4(x)

@end example

should plot functions f1, f2, f4 in your 3 newly defined line styles.
If a user-defined line style is not found then the corresponding default
linetype is used instead.  E.g. in the example above, f3(x) will be plotted
using the default linetype 3.


@node set_style_line, plotting_styles, set_style_increment, style
@subsubsection set style line

@c ?commands set style line
@c ?commands unset style line
@c ?commands show style line
@c ?set style line
@c ?unset style line
@c ?show style line
@cindex linestyle

@cindex linewidth

Each terminal has a default set of line and point types, which can be seen
by using the command @ref{test}.  `set style line` defines a set of line types
and widths and point types and sizes so that you can refer to them later by
an index instead of repeating all the information at each invocation.

Syntax:
@example
      set style line <index> default
      set style line <index> @{@{linetype  | lt@} <line_type> | <colorspec>@}
                             @{@{linecolor | lc@} <colorspec>@}
                             @{@{linewidth | lw@} <line_width>@}
                             @{@{pointtype | pt@} <point_type>@}
                             @{@{pointsize | ps@} <point_size>@}
                             @{palette@}
      unset style line
      show style line

@end example

If `default` is given all line style parameters are set to their default
values.

If the linestyle <index> already exists, only the given parameters are
changed while all others are preserved.  If not, all undefined values are
set to the default values.

The line and point types are taken from the default types for the terminal
currently in use.  The line width and point size are multipliers for the
default width and size (but note that <point_size> here is unaffected by
the multiplier given on @ref{pointsize}).

The defaults for the line and point types is the index.  The defaults for
the width and size are both unity.

Linestyles created by this mechanism do not replace the default linetype
styles; both may be used.  If you want plots to use the defined styles in
preference to the default linetypes, please see `set style increment`.

Not all terminals support the `linewidth` and @ref{pointsize} features; if
not supported, the option will be ignored.

Terminal-independent colors may be assigned using either
`linecolor <colorspec>` or `linetype <colorspec>`, abbreviated `lc` or `lt`.
This requires giving a RGB color triple, a known palette color name,
a fractional index into the current palette, or a constant value from the
current mapping of the palette onto cbrange.
See `colors`, @ref{colorspec}, @ref{palette}, @ref{colornames}, @ref{cbrange}.

`set style line <n> linetype <lt>` will set both a terminal-dependent dot/dash
pattern and color. The commands`set style line <n> linecolor <colorspec>` or
`set style line <n> linetype <colorspec>` will set a new line color while
leaving the existing dot-dash pattern unchanged.

In 3d mode (`splot` command), the special keyword @ref{palette} is allowed as a
shorthand for "linetype palette z".  The color value corresponds to the
z-value (elevation) of the splot, and varies smoothly along a line or surface.

Examples:
Suppose that the default lines for indices 1, 2, and 3 are red, green, and
blue, respectively, and the default point shapes for the same indices are a
square, a cross, and a triangle, respectively.  Then

@example
      set style line 1 lt 2 lw 2 pt 3 ps 0.5

@end example

defines a new linestyle that is green and twice the default width and a new
pointstyle that is a half-sized triangle.  The commands

@example
      set style function lines
      plot f(x) lt 3, g(x) ls 1

@end example

will create a plot of f(x) using the default blue line and a plot of g(x)
using the user-defined wide green line.  Similarly the commands

@example
      set style function linespoints
      plot p(x) lt 1 pt 3, q(x) ls 1

@end example

will create a plot of p(x) using the default triangles connected by a red
line and q(x) using small triangles connected by a green line.

@example
      splot sin(sqrt(x*x+y*y))/sqrt(x*x+y*y) w l pal

@end example

creates a surface plot using smooth colors according to @ref{palette}. Note,
that this works only on some terminals. See also @ref{palette}, @ref{pm3d}.

@example
      set style line 10 linetype 1 linecolor rgb "cyan"

@end example

will assign linestyle 10 to be a solid cyan line on any terminal that
supports rgb colors.


@node plotting_styles, set_style_rectangle, set_style_line, style
@subsubsection plotting styles

@c ?plotting styles

The commands `set style data` and `set style function` change the
default plotting style for subsequent `plot` and `splot` commands.

The types used for all line and point styles (i.e., solid, dash-dot, color,
etc. for lines; circles, squares, crosses, etc. for points) will be either
those specified on the `plot` or `splot` command or will be chosen
sequentially from the types available to the terminal in use.  Use the
command @ref{test} to see what is available.

None of the styles requiring more than two columns of information
(e.g., @ref{errorbars} or @ref{errorlines}) can be used with `splot`s or
function `plot`s. Neither `boxes`, `filledcurves` nor any
of the `steps` styles can be used with `splot`s. If an inappropriate style
is specified, it will be changed to `points`.

The above caveat does not apply to `plot with labels`, for which the third
column specifies a data source rather than coordinate information.
See `set style labels`.

For 2-d data with more than two columns, `gnuplot` is picky about the
allowed @ref{errorbars} and @ref{errorlines} styles. The @ref{using} option on the
`plot` command can be used to set up the correct columns for the style
you want. (In this discussion, "column" will be used to refer both to
a column in the data file and an entry in the @ref{using} list.)

For three columns, only `xerrorbars`, `yerrorbars` (or @ref{errorbars}),
`xerrorlines`, `yerrorlines` (or @ref{errorlines}), `boxes`,
and `boxerrorbars` are allowed. If another plot style is used, the style
will be changed to `yerrorbars`. The `boxerrorbars` style will
calculate the boxwidth automatically.

For four columns, only `xerrorbars`, `yerrorbars` (or @ref{errorbars}),
`xyerrorbars`, `xerrorlines`, `yerrorlines` (or @ref{errorlines}), `xyerrorlines`,
`boxxyerrorbars`, and `boxerrorbars` are allowed.  An illegal
style will be changed to `yerrorbars`.

Five-column data allow only the `boxerrorbars`, `financebars`, and
`candlesticks` styles.  An illegal style will be changed to `boxerrorbars`
before plotting.

Six- and seven-column data only allow the `xyerrorbars`,
`xyerrorlines`, and `boxxyerrorbars` styles. Illegal styles will be
changed to `xyerrorbars` before plotting.

For more information about error bars with and without lines,
please see @ref{errorlines} and @ref{errorbars}.


@node set_style_rectangle,  , plotting_styles, style
@subsubsection set style rectangle

@c ?commands set style rectangle
@c ?commands unset style rectangle
@c ?commands show style rectangle
@c ?set style rectangle
@c ?unset style rectangle
@c ?show style rectangle

Rectangles defined with the `set object rectangle` command can have individual
styles. However, if a rectangle is not assigned a private style then it
inherits a default that is taken from the `set style rectangle` command.

Syntax:
@example
    set style rectangle @{front|back@} @{fillcolor <colorspec>@} @{fs <fillstyle>@}
                        @{lw|linewidth <lw>@}

@end example

See @ref{colorspec} and `fillstyle`.  `fillcolor` may be abbreviated as `fc`.

Examples:
@example
    set style rectangle back fc rgb "white" fs solid 1.0 border -1
    set style rectangle fc linsestyle 3 fs pattern 2 noborder

@end example

The default values correspond to solid fill with the background color and a
black border.



@noindent --- BOXERRORBARS ---

@c ?commands set style boxerrorbars
@c ?set style boxerrorbars
@c ?plotting styles boxerrorbars
@c ?style boxerrorbars
@cindex boxerrorbars

The `boxerrorbars` style is only relevant to 2-d data plotting.  It is a
combination of the `boxes` and `yerrorbars` styles.  The boxwidth will come
from the fourth column if the y errors are in the form of "ydelta" and the
boxwidth was not previously set equal to -2.0 (`set boxwidth -2.0`) or from
the fifth column if the y errors are in the form of "ylow yhigh".  The
special case  `boxwidth = -2.0` is for four-column data with y errors in the
form "ylow yhigh".  In this case the boxwidth will be calculated so that each
box touches the adjacent boxes.  The width will also be calculated in cases
where three-column data are used.

The box height is determined from the y error in the same way as it is for
the `yerrorbars` style---either from y-ydelta to y+ydelta or from ylow to
yhigh, depending on how many data columns are provided.
See also
@uref{http://www.gnuplot.info/demo/mgr.html,errorbar demo.
}


@noindent --- BOXES ---

@c ?commands set style boxes
@c ?set style boxes
@c ?plotting styles boxes
@c ?style boxes
@cindex boxes

The `boxes` style is only relevant to 2-d plotting.  It draws a box centered
about the given x coordinate from the x axis (not the graph border) to the
given y coordinate.  The width of the box is obtained in one of three ways.
If it is a data plot and the data file has a third column, this will be used
to set the width of the box.  If not, if a width has been set using the @ref{boxwidth} command, this will be used.  If neither of these is available, the
width of each box will be calculated automatically so that it touches the
adjacent boxes.

The interior of the boxes is drawn according to the current fillstyle.
See `set style fill` for details.  Alternatively a new fillstyle
may be specified in the plot command.

For fillstyle `empty` the box is filled with the background color.

For fillstyle `solid` the box is filled with a solid rectangle of the
current drawing color. There is an optional parameter <density> that
controls the fill density; it runs from 0 (background color) to 1
(current drawing color).

For fillstyle `pattern` the box is filled in the current drawing color with
a pattern, if supported by the terminal driver.

Examples:

To plot a data file with solid filled boxes with a small vertical space
separating them (bargraph):

@example
      set boxwidth 0.9 relative
      set style fill solid 1.0
      plot 'file.dat' with boxes

@end example

To plot a sine and a cosine curve in pattern-filled boxes style:

@example
      set style fill pattern
      plot sin(x) with boxes, cos(x) with boxes

@end example

The sin plot will use pattern 0; the cos plot will use pattern 1.
Any additional plots would cycle through the patterns supported by the
terminal driver.

To specify explicit fillstyles for each dataset:

@example
     plot 'file1' with boxes fs solid 0.25, \
          'file2' with boxes fs solid 0.50, \
          'file3' with boxes fs solid 0.75, \
          'file4' with boxes fill pattern 1, \
          'file5' with boxes fill empty

@end example

Currently only the following terminal drivers support fillstyles other
than `empty`:
x11, windows, pm, wxt, postscript, fig, pbm, png, gif, hpdj, hppj, hpljii,
hp500c, jpeg, nec_cp6, epson_180dpi, epson_60dpi, epson_lx800, okidata, starc
and tandy_60dpi. The BeOS driver (`be`) is untested.


@noindent --- BOXXYERRORBARS ---

@c ?commands set style boxxyerrorbars
@c ?set style boxxyerrorbars
@c ?plotting styles boxxyerrorbars
@c ?style boxxyerrorbars
@cindex boxxyerrorbars

The `boxxyerrorbars` style is only relevant to 2-d data plotting.  It is a
combination of the `boxes` and `xyerrorbars` styles.

The box width and height are determined from the x and y errors in the same
way as they are for the `xyerrorbars` style---either from xlow to xhigh and
from ylow to yhigh, or from x-xdelta to x+xdelta and from y-ydelta to
y+ydelta , depending on how many data columns are provided.

If filled-box support is present, then the interior of the boxes is drawn
according to the current fillstyle.  See `set style fill` and `boxes` for
details.  Alternatively a new fillstyle may be specified in the plot command.


@noindent --- CANDLESTICKS ---

@c ?commands set style candlesticks
@c ?set style candlesticks
@c ?plotting styles candlesticks
@c ?style candlesticks
@cindex candlesticks

The `candlesticks` style can be used for 2-d data plotting of financial
data or for generating box-and-whisker plots of statistical data.
Five columns of data are required; in order, these should be the x
coordinate (most likely a date) and the opening, low, high, and closing
prices.  The symbol is a rectangular box, centered horizontally at the x
coordinate and limited vertically by the opening and closing prices.  A
vertical line segment at the x coordinate extends up from the top of the
rectangle to the high price and another down to the low.  The vertical line
will be unchanged if the low and high prices are interchanged.

The width of the rectangle can be controlled by the @ref{boxwidth} command.
For backwards compatibility with earlier gnuplot versions, when the
boxwidth parameter has not been set then the width of the candlestick
rectangle is controlled by `set bars <width>`.

By default the vertical line segments have no crossbars at the top and
bottom. If you want crossbars, which are typically used for box-and-whisker
plots, then add the keyword `whiskerbars` to the plot command.  By default
these whiskerbars extend the full horizontal width of the candlestick, but
you can modify this by specifying a fraction of the full width.

By default the rectangle is empty if (open < close), and filled with three
vertical bars if (close < open). If filled-boxes support is present, then
the rectangle is colored according to `set style fill <fillstyle>`.
See @ref{bars} and `financebars`.  See also
@uref{http://gnuplot.sourceforge.net/demo/candlesticks.html,finance demos
}
.

Note: To place additional symbols, such as the median value, on a
box-and-whisker plot requires additional plot commands as in this example:

@example
  # Data columns: X Min 1stQuartile Median 3rdQuartile Max
  set bars 4.0
  set style fill empty
  plot 'stat.dat' using 1:3:2:6:5 with candlesticks title 'Quartiles', \
       ''         using 1:4:4:4:4 with candlesticks lt -1 notitle

@end example

@example
  # Plot with crossbars on the whiskers, crossbars are 50% of full width
  plot 'stat.dat' using 1:3:2:6:5 with candlesticks whiskerbars 0.5

@end example

@example
 See @ref{boxwidth}, @ref{bars} and `set style fill`.

@end example


@noindent --- DOTS ---

@c ?commands set style dots
@c ?set style dots
@c ?plotting styles dots
@c ?style dots
@cindex dots

The `dots` style plots a tiny dot at each point; this is useful for scatter
plots with many points. For some terminals (post, pdf) the size of the dot can
be controlled by changing the linewidth.


@noindent --- FILLEDCURVES ---

@c ?commands set style filledcurves
@c ?set style filledcurves
@c ?plotting styles filledcurves
@c ?style filledcurves
@cindex filledcurves

The `filledcurves` style is only relevant to 2-d plotting. Three variants
are possible. The first two variants require either a function or two columns
of input data, and may be further modified by the options listed below.
The first variant, `closed`, treats the curve itself as a closed polygon.
This is the default if there are two columns of input data.

The second variant is to fill the area between the curve and a given axis,
a horizontal or vertical line, or a point.

The third variant requires three columns of input data: the x coordinate and
two y coordinates corresponding to two curves sampled at the same set of
x coordinates; the area between the two curves is filled.
This is the default if there are three or more columns of input data.

Syntax:

@example
    set style [data | function] filledcurves [option]
    plot ... with filledcurves [option]

@end example

where the option can be

@example
    [closed | @{above | below@} @{x1 | x2 | y1 | y2@}[=<a>] | xy=<x>,<y>]

@end example

The first two plot variants can be further modified by the options

@example
    filledcurves closed   ... just filled closed curve,
    filledcurves x1       ... x1 axis,
    filledcurves x2       ... x2 axis, etc for y1 and y2 axes,
    filledcurves y1=0     ... line y=0 (at y1 axis) ie parallel to x1 axis,
    filledcurves y2=42    ... line y=42 (at y2 axis) ie parallel to x2, etc,
    filledcurves xy=10,20 ... point 10,20 of x1,y1 axes (arc-like shape).

@end example

Example of filling the area between two input curves.
@uref{http://www.gnuplot.info/demo/fillbetween.html,fill between curves demo.
}

@example
    plot 'data' using 1:2:3 with filledcurves

@end example

The `above` and `below` options apply both to commands of the form
@example
    ... filledcurves above @{x1|x2|y1|y2@}=<val>
@end example

and to commands of the form
@example
    ... using 1:2:3 with filledcurves below
@end example

In either case the option limits the filled area to one side of the bounding
line or curve.

Note: Not all terminal types support this plotting mode.

Zoom of a filled curve drawn from a datafile may produce empty or incorrect
area because gnuplot is clipping points and lines, and not areas.

If the values of <a>, <x>, <y> are out of the drawing boundary, then they
are moved to the graph boundary. Then the actually filled area in the case
of option xy=<x>,<y> will depend on xrange and yrange.


@noindent --- FINANCEBARS ---

@c ?commands set style financebars
@c ?set style financebars
@c ?plotting styles financebars
@c ?style financebars
@cindex financebars

The `financebars` style is only relevant for 2-d data plotting of financial
data.  Five columns of data are required; in order, these should be the x
coordinate (most likely a date) and the opening, low, high, and closing
prices.  The symbol is a vertical line segment, located horizontally at the x
coordinate and limited vertically by the high and low prices.  A horizontal
tic on the left marks the opening price and one on the right marks the
closing price.  The length of these tics may be changed by @ref{bars}.  The
symbol will be unchanged if the high and low prices are interchanged.
See @ref{bars} and `candlesticks`, and also the
@uref{http://www.gnuplot.info/demo/finance.html,finance demo.
}


@noindent --- FSTEPS ---

@c ?commands set style fsteps
@c ?set style fsteps
@c ?plotting styles fsteps
@c ?style fsteps
@cindex fsteps

The `fsteps` style is only relevant to 2-d plotting.  It connects consecutive
points with two line segments: the first from (x1,y1) to (x1,y2) and the
second from (x1,y2) to (x2,y2).
See also
@uref{http://www.gnuplot.info/demo/steps.html,steps demo.
}


@noindent --- HISTEPS ---

@c ?commands set style histeps
@c ?set style histeps
@c ?plotting styles histeps
@c ?style histeps
@cindex histeps

The `histeps` style is only relevant to 2-d plotting.  It is intended for
plotting histograms.  Y-values are assumed to be centered at the x-values;
the point at x1 is represented as a horizontal line from ((x0+x1)/2,y1) to
((x1+x2)/2,y1).  The lines representing the end points are extended so that
the step is centered on at x.  Adjacent points are connected by a vertical
line at their average x, that is, from ((x1+x2)/2,y1) to ((x1+x2)/2,y2).

If @ref{autoscale} is in effect, it selects the xrange from the data rather than
the steps, so the end points will appear only half as wide as the others.
See also
@uref{http://www.gnuplot.info/demo/steps.html,steps demo.
}

`histeps` is only a plotting style; `gnuplot` does not have the ability to
create bins and determine their population from some data set.


@noindent --- HISTOGRAMS ---

@c ?commands set style histogram
@c ?set style histogram
@c ?style histograms
@c ?plotting styles histograms
@cindex histograms

The `histograms` style is only relevant to 2-d plotting.  It produces a bar
chart from a sequence of data columns in parallel. Each element of the
`plot` command must specify a single input data source (e.g. one column of
the input file), possibly with associated tic values or key titles.
Four styles of histogram layout are currently supported.

@example
      set style histogram clustered @{gap <gapsize>@}
      set style histogram errorbars @{gap <gapsize>@} @{<linewidth>@}
      set style histogram rowstacked
      set style histogram columnstacked

@end example

The default style corresponds to `set style histogram clustered gap 2`.
In this style, each set of parallel data values is collected into a group of
boxes clustered at the x-axis coordinate corresponding to their sequential
position (row #) in the selected datafile columns.  Thus if <n> datacolumns are
selected, the first cluster is centered about x=1, and contains <n> boxes whose
heights are taken from the first entry in the corresponding <n> data columns.
This is followed by a gap and then a second cluster of boxes centered about x=2
corresponding to the second entry in the respective data columns, and so on.
The default gap width of 2 indicates that the empty space between clusters is
equivalent to the width of 2 boxes.  All boxes derived from any one column
are given the same fill color and/or pattern (see `set style fill`).

Each cluster of boxes is derived from a single row of the input data file.
It is common in such input files that the first element of each row is a
label. Labels from this column may be placed along the x-axis underneath
the appropriate cluster of boxes with the `xticlabels` option to @ref{using}.

The @ref{errorbars} style is very similar to the `clustered` style, except that
it requires two columns of input for each entry. The first column is treated
as the height (y-value) of that box, exactly as for the `clustered` style.
The second column is treated as an error magnitude, and used to generate a
vertical error bar at the top of the box. The appearance of the error bar is
controlled by the current value of @ref{bars} and by the optional <linewidth>
specification.

Two styles of stacked histogram are supported, chosen by the command
`set style histogram @{rowstacked|columnstacked@}`.  In these styles the data
values from the selected columns are collected into stacks of boxes.
Positive values stack upwards from y=0; negative values stack downwards.
Mixed positive and negative values will produce both an upward stack and a
downward stack.  The default stacking mode is `rowstacked`.

The `rowstacked` style places a box resting on the x-axis for each
data value in the first selected column; the first data value results in
a box a x=1, the second at x=2, and so on.  Boxes corresponding to the
second and subsequent data columns are layered on top of these, resulting
in a stack of boxes at x=1 representing the first data value from each
column, a stack of boxes at x=2 representing the second data value from
each column, and so on.  All boxes derived from any one column are given the
same fill color and/or pattern (see `set style fill`).

The `columnstacked` style is similar, except that each stack of boxes is
built up from a single data column. Each data value from the first specified
column yields a box in the stack at x=1, each data value from the second
specified column yields a box in the stack at x=2, and so on.  In this style
the color of each box is taken from the row number, rather than the column
number, of the corresponding data field.

Box widths may be modified using the @ref{boxwidth} command.
Box fill styles may be set using the `set style fill` command.

Histograms always use the x1 axis, but may use either y1 or y2.
If a plot contains both histograms and other plot styles, the non-histogram
plot elements may use either the x1 or the x2 axis.

Examples:

To plot a data file containing multiple columns of data as a histogram
of clustered boxes (the default style):

@example
      set boxwidth 0.9 relative
      set style data histograms
      set style fill solid 1.0 border -1
      plot 'file.dat' using 2, '' using 4, '' using 6

@end example

This will produce a plot with clusters of three boxes (vertical bars) centered
at each integral value on the x axis.  If the first column of the input file
contains labels, they may be placed along the x-axis using the variant command

@example
      plot 'file.dat' using 2, '' using 4, '' using 6:xticlabels(1)

@end example

If the file contains both a magnitude and an error estimate for each value,
then error bars can be added to the plot.  The following commands will add
error bars extending from (y-<error>) to (y+<error>), capped by horizontal bar
ends drawn the same width as the box itself. The error bars and bar ends are
drawn with linewidth 2 using the border linetype from the current fill style.

@example
      set bars fullwidth
      set style fill solid border -1
      set style histogram errorbars gap 2 lw 2
      plot 'file.dat' using 2:3, '' using 4:5, '' using 6:7:xticlabels(1)

@end example

To plot the same data as a rowstacked histogram:

@example
      set style histogram rows
      plot 'file.dat' using 2, '' using 4, '' using 6:xtic(1)

@end example

This will produce a plot in which each vertical bar contains a stack of three
segments, corresponding in height to the values found in columns 2, 4 and 6
of the datafile.

Finally, the commands

@example
      set style histogram columnstacked
      plot 'file.dat' using 2, '' using 4, '' using 6

@end example

will produce three vertical stacks. The stack at x=1 will contain a box for
each entry in column 2 of the datafile.  The stack at x=2 will contain a box
for each parallel entry in column 4 of the datafile, and the stack at x=3 a
box for each entry of column 6.  Because this interchanges gnuplot's usual
interpretation of input rows and columns, the specification of key titles and
x-axis tic labels must also be modified.

@example
      set style histogram columnstacked
      plot '' u 5:key(1)            # uses first column to generate key titles
      plot '' u 5 title columnhead  # uses first row to generate xtic labels

@end example


@noindent --- NEWHISTOGRAM ---

@cindex newhistogram

@c ?histograms newhistogram
More than one set of histograms can appear in a single plot. In this case you
can force a gap between them, and a separate label for each set, by using the
plot command `newhistogram @{"<title>"@} @{<linetype>@} @{at <x-coord>@}`.
For example

@example
      set style histogram  cluster
      plot newhistogram "Set A", 'a' using 1, '' using 2, '' using 3, \
           newhistogram "Set B", 'b' using 1, '' using 2, '' using 3

@end example

The labels "Set A" and "Set B" will appear beneath the respective sets of
histograms, under the overall x axis label.

The newhistogram command can also be used to force histogram coloring to
begin with a specific color (linetype). By default colors will continue to
increment successively even across histogram boundaries. Here is an example
using the same coloring for multiple histograms
@example
      plot newhistogram "Set A" lt 4, 'a' using 1, '' using 2, '' using 3, \
           newhistogram "Set B" lt 4, 'b' using 1, '' using 2, '' using 3

@end example

The `at <x-coord>` option only applies to column-stacked histograms.


@noindent --- IMAGE ---

@c ?commands set style image
@c ?set style image
@c ?plotting styles image
@c ?style image
@cindex image

The `image` style is intendend for plotting 2D images.  It may be used for
both `plot` and `splot` in the form of 3D data (x,y,value) or projected 4D
data (x,y,z,value), respectively.  It is assumed that in the viewing plane
the image data forms an equidistant sampling grid in the viewing plane along
two, not necessarily  orthogonal, directions.  In other words, groups of
four adjacent points are assumed to form the same size parallelogram.  The
variable `value` in the tuples represent a palette color (gray value) for
indexing in the current palette.

The `image` style will attempt to create a properly positioned and scaled
data matrix to match the plot borders for those terminals supporting palettes
and images.  Such output is efficient and draws quickly.  However, when a
terminal driver does not support palettes and images, or when image support
is not implemented, the `image` style reverts to drawing filled rectangular
boxes for pixels, which is not as efficient.  General parallelogram-shaped
images currently always have filled parallelograms for pixels.

The coordinate of each data point of an image will lie at the center of a
pixel.  That is, an M x N set of data will form an image with M x N pixels.
This is slightly different than pm3d elements where an M x N set of data
will form a surface of (M-1) x (N-1) elements.  The scan directions for the
image data grid can be any of eight possible combinations.

Here are some specific comments about particular terminal drivers:

x11 and wxt - Pixels are either repeated or decimated to fit the display
@example
      resolution; no other processing (filtering) is done.  Thus, aliasing may
      occur when decimating images having high spatial frequency content.

@end example

postscript (pslatex, epslatex, pstex) - Image is copied in its original
@example
      resolution, and sample interpolation is turned off.

@end example

See also `rgbimage`.


@noindent --- IMPULSES ---

@c ?commands set style impulses
@c ?set style impulses
@c ?plotting styles impulses
@c ?style impulses
@cindex impulses

The `impulses` style displays a vertical line from the x axis (not the graph
border), or from the grid base for `splot`, to each point.


@noindent --- LABELS ---

@c ?commands set style labels
@c ?set style labels
@c ?plotting styles labels
@c ?style labels
@cindex labels

The `labels` style is available only if gnuplot is built with configuration
option --enable-datastrings. For a 2-D plot with labels you must specify
3 input data columns; the text string found in the third column is printed at
the X and Y coordinates generated by the first two column specifiers. The
font, color, rotation angle and other properties of the printed text may be
specified as additional command options (see @ref{label}). The example below
will generate a 2-D plot with text labels taken from column 4 of the input
file (`tc lt 2` is shorthand for `textcolor linetype 2`, which is green).

@example
  plot 'datafile' using 1:(0.5 * $2):4 with labels font "arial,11" tc lt 2

@end example

The `labels` style can also be used in 3-D plots. In this case four input
column specifiers are required, corresponding to X Y Z and text.

@example
  splot 'datafile' using 1:2:3:4 with labels

@end example

See also `datastrings`, `set style data`.


@noindent --- LINES ---

@c ?commands set style lines
@c ?set style lines
@c ?plotting styles lines
@c ?style lines
@cindex lines

The `lines` style connects adjacent points with straight line segments.
See also `linetype`, `linewidth`, and `linestyle`.


@noindent --- LINESPOINTS ---

@c ?commands set style linespoints
@c ?commands set style lp
@c ?set style linespoints
@c ?plotting styles linespoints
@c ?set style lp
@c ?style linespoints
@c ?style lp
@cindex linespoints

@cindex lp

The `linespoints` style does both `lines` and `points`, that is, it draws a
small symbol at each point and then connects adjacent points with straight
line segments.  The command @ref{pointsize} may be used to change the size of
the points.  See @ref{pointsize} for its usage.

`linespoints` may be abbreviated `lp`.


@noindent --- POINTS ---

@c ?commands set style points
@c ?set style points
@c ?plotting styles points
@c ?style points
@cindex points

The `points` style displays a small symbol at each point.  The command @ref{pointsize} may be used to change the size of the points.  See @ref{pointsize}
for its usage.


@noindent --- STEPS ---

@c ?commands set style steps
@c ?set style steps
@c ?plotting styles steps
@c ?style steps
@cindex steps

The `steps` style is only relevant to 2-d plotting.  It connects consecutive
points with two line segments: the first from (x1,y1) to (x2,y1) and the
second from (x2,y1) to (x2,y2).
See also
@uref{http://www.gnuplot.info/demo/steps.html,steps demo.
}


@noindent --- RGBIMAGE ---

@c ?commands set style rgbimage
@c ?set style rgbimage
@c ?plotting styles rgbimage
@c ?style rgbimage
@cindex rgbimage

The `rgbimage` style is intended for plotting 2D images and is similar
in concept to `image`.  See `image` for details.  The difference is
that 5D data (x,y,r,g,b) for `plot` and 6D data (x,y,z,r,g,b) for `splot`
describe the coordinates and color components of an image.

See also `image`.


@noindent --- VECTORS ---

@c ?commands set style vectors
@c ?set style vectors
@c ?plotting styles vectors
@c ?style vectors
@cindex vectors

The 2D `vectors` style draws a vector from (x,y) to (x+xdelta,y+ydelta).
Thus it requires four columns of data.  It also draws a small arrowhead at the
end of the vector.
The 3D `vectors` style is similar, but requires six columns of data.
splot with vectors is supported only for `set mapping cartesian`.
The keywords "with vectors" may be followed by arrow style specifications.
See `arrowstyle` for more details.

Example:
@example
      plot 'file.dat' using 1:2:3:4 with vectors head filled lt 2
      splot 'file.dat' using 1:2:3:(1):(1):(1) with vectors filled head lw 2

@end example

`set clip one` and `set clip two` affect vectors drawn in 2D.
Please see @ref{clip} and `arrowstyle`.


@noindent --- XERRORBARS ---

@c ?commands set style xerrorbars
@c ?set style xerrorbars
@c ?plotting styles xerrorbars
@c ?style xerrorbars
@cindex xerrorbars

The `xerrorbars` style is only relevant to 2-d data plots.  `xerrorbars` is
like `dots`, except that a horizontal error bar is also drawn.  At each point
(x,y), a line is drawn from (xlow,y) to (xhigh,y) or from (x-xdelta,y) to
(x+xdelta,y), depending on how many data columns are provided.  A tic mark
is placed at the ends of the error bar (unless @ref{bars} is used---see
@ref{bars} for details).


@noindent --- XYERRORBARS ---

@c ?commands set style xyerrorbars
@c ?set style xyerrorbars
@c ?plotting styles xyerrorbars
@c ?style xyerrorbars
@cindex xyerrorbars

The `xyerrorbars` style is only relevant to 2-d data plots.  `xyerrorbars` is
like `dots`, except that horizontal and vertical error bars are also drawn.
At each point (x,y), lines are drawn from (x,y-ydelta) to (x,y+ydelta) and
from (x-xdelta,y) to (x+xdelta,y) or from (x,ylow) to (x,yhigh) and from
(xlow,y) to (xhigh,y), depending upon the number of data columns provided.  A
tic mark is placed at the ends of the error bar (unless @ref{bars} is
used---see @ref{bars} for details).

If data are provided in an unsupported mixed form, the @ref{using} filter on the
`plot` command should be used to set up the appropriate form.  For example,
if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use

@example
      plot 'data' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars

@end example


@noindent --- YERRORBARS ---

@c ?commands set style yerrorbars
@c ?commands set style errorbars
@c ?plotting styles yerrorbars
@c ?plotting styles errorbars
@c ?set style yerrorbars
@c ?set style errorbars
@c ?style yerrorbars
@c ?style errorbars
@cindex yerrorbars

The `yerrorbars` (or @ref{errorbars}) style is only relevant to 2-d data plots.
`yerrorbars` is like `points`, except that a vertical error bar is also drawn.
At each point (x,y), a line is drawn from (x,y-ydelta) to (x,y+ydelta) or
from (x,ylow) to (x,yhigh), depending on how many data columns are provided.
A tic mark is placed at the ends of the error bar (unless @ref{bars} is
used---see @ref{bars} for details).
See also
@uref{http://www.gnuplot.info/demo/mgr.html,errorbar demo.
}


@noindent --- XERRORLINES ---

@c ?commands set style xerrorlines
@c ?set style xerrorlines
@c ?plotting styles xerrorlines
@c ?style xerrorlines
@cindex xerrorlines

The `xerrorlines` style is only relevant to 2-d data plots.
`xerrorlines` is like `linespoints`, except that a horizontal error
line is also drawn. At each point (x,y), a line is drawn from (xlow,y)
to (xhigh,y) or from (x-xdelta,y) to (x+xdelta,y), depending on how
many data columns are provided. A tic mark is placed at the ends of
the error bar (unless @ref{bars} is used---see @ref{bars} for details).


@noindent --- XYERRORLINES ---

@c ?commands set style xyerrorlines
@c ?set style xyerrorlines
@c ?plotting styles xyerrorlines
@c ?style xyerrorlines
@cindex xyerrorlines

The `xyerrorlines` style is only relevant to 2-d data plots.
`xyerrorlines` is like `linespoints`, except that horizontal and
vertical error bars are also drawn. At each point (x,y), lines are
drawn from (x,y-ydelta) to (x,y+ydelta) and from (x-xdelta,y) to
(x+xdelta,y) or from (x,ylow) to (x,yhigh) and from (xlow,y) to
(xhigh,y), depending upon the number of data columns provided. A tic
mark is placed at the ends of the error bar (unless @ref{bars} is
used---see @ref{bars} for details).

If data are provided in an unsupported mixed form, the @ref{using} filter on the
`plot` command should be used to set up the appropriate form.  For example,
if the data are of the form (x,y,xdelta,ylow,yhigh), then you can use

@example
      plot 'data' using 1:2:($1-$3):($1+$3):4:5 with xyerrorlines

@end example


@noindent --- YERRORLINES ---

@c ?commands set style yerrorlines
@c ?commands set style errorlines
@c ?plotting styles yerrorlines
@c ?plotting styles errorlines
@c ?set style yerrorlines
@c ?set style errorlines
@c ?style yerrorlines
@c ?style errorlines
@cindex yerrorlines

The `yerrorlines` (or @ref{errorlines}) style is only relevant to 2-d data
plots. `yerrorlines` is like `linespoints`, except that a vertical
error line is also drawn. At each point (x,y), a line is drawn from
(x,y-ydelta) to (x,y+ydelta) or from (x,ylow) to (x,yhigh), depending
on how many data columns are provided. A tic mark is placed at the
ends of the error bar (unless @ref{bars} is used---see @ref{bars} for
details).
See also
@uref{http://www.gnuplot.info/demo/mgr.html,errorbar demo.
}

@node surface, table, style, set-show
@subsection surface

@c ?commands set surface
@c ?commands unset surface
@c ?commands show surface
@c ?set surface
@c ?unset surface
@c ?show surface
@cindex surface
@opindex surface


@cindex nosurface

The command @ref{surface} controls the display of surfaces by `splot`.

Syntax:
@example
      set surface
      unset surface
      show surface

@end example

The surface is drawn with the style specified by @ref{with}, or else the
appropriate style, data or function.

Whenever @ref{surface} is issued, `splot` will not draw points or lines
corresponding to the function or data file points.  Contours may still be
drawn on the surface, depending on the @ref{contour} option. `unset surface;
set contour base` is useful for displaying contours on the grid base.  See
also @ref{contour}.

@node table, terminal, surface, set-show
@subsection table

@c ?commands set table
@c ?set table
@cindex table
@opindex table


When @ref{table} mode is enabled, `plot` and `splot` commands print out a
multicolumn ASCII table of X Y @{Z@} R values rather than creating an actual
plot on the current terminal.  The character R takes on one of three values:
"i" if the point is in the active range, "o" if it is out-of-range, or "u"
if it is undefined.  The data format is determined by the format of the axis
labels (see `set format`), and the columns are separated by single spaces.
This can be useful if you want to generate contours and then save them for
further use, perhaps for plotting with `plot`;  see @ref{contour} for example.
The same method can be used to save interpolated data
(see @ref{samples} and @ref{dgrid3d}).

Syntax:
@example
      set table @{"outfile"@}
      plot <whatever>
      unset table

@end example

Tabular output is written to the named file, if any, otherwise it is written
to the current value of @ref{output}.  You must explicitly @ref{table}
in order to go back to normal plotting on the current terminal.

@node terminal, termoption, table, set-show
@subsection terminal

@c ?commands set terminal
@c ?commands show terminal
@c ?set terminal
@c ?set term
@c ?show terminal
@c ?show term
@c ?set terminal push
@c ?set term push
@c ?terminal push
@c ?term push
@cindex push

@c ?set terminal pop
@c ?set term pop
@c ?terminal pop
@c ?term pop
@cindex pop

`gnuplot` supports many different graphics devices.  Use @ref{terminal} to
tell `gnuplot` what kind of output to generate. Use @ref{output} to redirect
that output to a file or device.

Syntax:
@example
      set terminal @{<terminal-type> | push | pop@}
      show terminal

@end example

If <terminal-type> is omitted, `gnuplot` will list the available terminal
types.  <terminal-type> may be abbreviated.

If both @ref{terminal} and @ref{output} are used together, it is safest to
give @ref{terminal} first, because some terminals set a flag which is needed
in some operating systems.

Several terminals have many additional options.  For example, see `png`,
or @ref{postscript}.
The options used by a previous invocation `set term <term> <options>` of a
given `<term>` are remembered, thus subsequent `set term <term>` does
not reset them.  This helps in printing, for instance, when switching
among different terminals---previous options don't have to be repeated.

The command `set term push` remembers the current terminal including its
settings while `set term pop` restores it. This is equivalent to `save term`
and `load term`, but without accessing the filesystem. Therefore they can be
used to achieve platform independent restoring of the terminal after printing,
for instance. After gnuplot's startup, the default terminal or that from
`startup` file is pushed automatically. Therefore portable scripts can rely
that `set term pop` restores the default terminal on a given platform unless
another terminal has been pushed explicitly.

For a complete list of available terminal types, see @ref{terminal}.

@node termoption, tics, terminal, set-show
@subsection termoption

@c ?commands set termoption
@c ?set termoption
@cindex termoption
@opindex termoption


The @ref{termoption} command allows you to change the behaviour of the
current terminal without requiring a new @ref{terminal} command. Only one
option can be changed per command, and only a small number of options can
be changed this way. Currently the only options accepted are

@example
     set termoption @{no@}enhanced
     set termoption font "<fontname>@{,<fontsize>@}"

@end example


@node tics, ticslevel, termoption, set-show
@subsection tics

@c ?commands set tics
@c ?commands unset tics
@c ?commands show tics
@c ?set tics
@c ?unset tics
@c ?show tics
@cindex tics
@opindex tics


Control of the major (labelled) tics on all axes at once is possible with the
`set tics` command.

Fine control of the major (labelled) tics on all axes at once is possible
with the `set tics` command.  The tics may be turned off with the `unset tics`
command, and may be turned on (the default state) with `set tics`.  Similar
commands (by preceding 'tics' by the axis name) control the major tics on a
single axis.

Syntax:
@example
      set tics @{axis | border@} @{@{no@}mirror@}
               @{in | out@} @{scale @{default | <major> @{,<minor>@}@}@}
               @{@{no@}rotate @{by <ang>@}@} @{offset <offset> | nooffset@}
               @{ format "formatstring" @} @{ font "name@{,<size>@}" @}
               @{ textcolor <colorspec> @}
      set tics @{front | back@}
      unset tics
      show tics

@end example

The options in the first set above can be applied individually to 
any or all axes, i.e., x, y, z, x2, y2, and cb.

Set tics `front` or `back` applies to all axes at once, but only for 2D plots
(not splot).  It controls whether the tics are placed behind or in front of
the plot elements, in the case that there is overlap.

`axis` or @ref{border} tells `gnuplot` to put the tics (both the tics themselves
and the accompanying labels) along the axis or the border, respectively.  If
the axis is very close to the border, the `axis` option will move the
tic labels to outside the border in case the border is printed (see
@ref{border}).  The relevant margin settings will usually be sized badly by
the automatic layout algorithm in this case.

`mirror` tells `gnuplot` to put unlabelled tics at the same positions on the
opposite border.  `nomirror` does what you think it does.

`in` and `out` change the tic marks to be drawn inwards or outwards.

With `scale`, the size of the tic marks can be adjusted. If <minor> is not
specified, it is 0.5*<major>.  The default size 1.0 for major tics and 0.5
for minor tics is requested by `scale default`.

`rotate` asks `gnuplot` to rotate the text through 90 degrees, which will be
done if the terminal driver in use supports text rotation.  `norotate`
cancels this. `rotate by <ang>` asks for rotation by <ang> degrees, supported
by some terminal types.

The defaults are `border mirror norotate` for tics on the x and y axes, and
`border nomirror norotate` for tics on the x2 and y2 axes.  For the z axis,
the default is `nomirror`.

The <offset> is specified by either x,y or x,y,z, and may be preceded by
`first`, `second`, `graph`, `screen`, or `character` to select the
coordinate system. <offset> is the offset of the tics texts from their
default positions, while the default coordinate system is `character`.
See `coordinates` for details. `nooffset` switches off the offset.

`set tics` with no options restores to place tics inwards. Every other
options are retained.

See also `set xtics` for more control of major (labelled) tic marks and
@ref{mxtics} for control of minor tic marks.  These commands provide control
at a axis by axis basis.

@node ticslevel, ticscale, tics, set-show
@subsection ticslevel

See @ref{xyplane}.

@node ticscale, timestamp, ticslevel, set-show
@subsection ticscale

@c ?commands set ticscale
@c ?commands show ticscale
@c ?set ticscale
@c ?show ticscale
@cindex ticscale
@opindex ticscale


The @ref{ticscale} command is deprecated, use `set tics scale` instead.

@node timestamp, timefmt, ticscale, set-show
@subsection timestamp

@c ?commands set timestamp
@c ?commands unset timestamp
@c ?commands show timestamp
@c ?set timestamp
@c ?unset timestamp
@c ?show timestamp
@cindex timestamp
@opindex timestamp


@cindex notimestamp

The command @ref{timestamp} places the time and date of the plot in the left
margin.

Syntax:
@example
      set timestamp @{"<format>"@} @{top|bottom@} @{@{no@}rotate@}
                    @{offset <xoff>@{,<yoff>@}@} @{font "<fontspec>"@}
      unset timestamp
      show timestamp

@end example

The format string allows you to choose the format used to write the date and
time.  Its default value is what asctime() uses: "%a %b %d %H:%M:%S %Y"
(weekday, month name, day of the month, hours, minutes, seconds, four-digit
year).  With `top` or `bottom` you can place the timestamp at the top or
bottom of the left margin (default: bottom).  `rotate` lets you write the
timestamp vertically, if your terminal supports vertical text.  The constants
<xoff> and <yoff> are offsets that let you adjust the position more finely.
<font> is used to specify the font with which the time is to be written.

The abbreviation `time` may be used in place of @ref{timestamp}.

Example:
@example
      set timestamp "%d/%m/%y %H:%M" offset 80,-2 font "Helvetica"

@end example

See @ref{timefmt} for more information about time format strings.

@node timefmt, title_, timestamp, set-show
@subsection timefmt

@c ?commands set timefmt
@c ?commands show timefmt
@c ?set timefmt
@c ?show timefmt
@cindex timefmt
@opindex timefmt


This command applies to timeseries where data are composed of dates/times.
It has no meaning unless the command `set xdata time` is given also.

Syntax:
@example
      set timefmt "<format string>"
      show timefmt

@end example

The string argument tells `gnuplot` how to read timedata from the datafile.
The valid formats are:


@example
      Format       Explanation
      %d           day of the month, 1--31
      %m           month of the year, 1--12
      %y           year, 0--99
      %Y           year, 4-digit
      %j           day of the year, 1--365
      %H           hour, 0--24
      %M           minute, 0--60
      %s           seconds since the Unix epoch (1970-01-01, 00:00 UTC)
      %S           second, 0--60
      %b           three-character abbreviation of the name of the month
      %B           name of the month

@end example

Any character is allowed in the string, but must match exactly.  \t (tab) is
recognized.  Backslash-octals (\nnn) are converted to char.  If there is no
separating character between the time/date elements, then %d, %m, %y, %H, %M
and %S read two digits each, %Y reads four digits and %j reads three digits.
%b requires three characters, and %B requires as many as it needs.

Spaces are treated slightly differently.  A space in the string stands for
zero or more whitespace characters in the file.  That is, "%H %M" can be used
to read "1220" and "12     20" as well as "12 20".

Each set of non-blank characters in the timedata counts as one column in the
`using n:n` specification.  Thus `11:11  25/12/76  21.0` consists of three
columns.  To avoid confusion, `gnuplot` requires that you provide a complete
@ref{using} specification if your file contains timedata.

Since `gnuplot` cannot read non-numerical text, if the date format includes
the day or month in words, the format string must exclude this text.  But
it can still be printed with the "%a", "%A", "%b", or "%B" specifier:
see `set format` for more details about these and other options for printing
timedata.  (`gnuplot` will determine the proper month and weekday from the
numerical values.)

See also @ref{xdata} and `Time/date` for more information.

Example:
@example
      set timefmt "%d/%m/%Y\t%H:%M"
@end example

tells `gnuplot` to read date and time separated by tab.  (But look closely at
your data---what began as a tab may have been converted to spaces somewhere
along the line; the format string must match what is actually in the file.)
See also
@uref{http://www.gnuplot.info/demo/timedat.html,time data demo.
}

@node title_, tmargin, timefmt, set-show
@subsection title

@c ?commands set title
@c ?commands show title
@c ?set title
@c ?show title
@cindex title
@opindex title


The @ref{title} command produces a plot title that is centered at the top of
the plot.  @ref{title} is a special case of @ref{label}.

Syntax:
@example
      set title @{"<title-text>"@} @{offset <offset>@} @{font "<font>@{,<size>@}"@}
                @{@{textcolor | tc@} @{<colorspec> | default@}@} @{@{no@}enhanced@}
      show title

@end example

If <offset> is specified by either x,y or x,y,z the title is moved by the
given offset.  It may be preceded by `first`, `second`, `graph`, `screen`,
or `character` to select the coordinate system.  See `coordinates` for
details.  By default, the `character` coordinate system is used.  For
example, "`set title offset 0,-1`" will change only the y offset of the
title, moving the title down by roughly the height of one character.  The
size of a character depends on both the font and the terminal.

<font> is used to specify the font with which the title is to be written;
the units of the font <size> depend upon which terminal is used.

`textcolor <colorspec>` changes the color of the text. <colorspec> can be a
linetype, an rgb color, or a palette mapping. See help for @ref{colorspec} and
@ref{palette}.

`noenhanced` requests that the title not be processed by the enhanced text
mode parser, even if enhanced text mode is currently active.

@ref{title} with no parameters clears the title.

See `syntax` for details about the processing of backslash sequences and
the distinction between single- and double-quotes.

@node tmargin, trange, title_, set-show
@subsection tmargin

@c ?commands set tmargin
@c ?set tmargin
@cindex tmargin
@opindex tmargin


The command @ref{tmargin} sets the size of the top margin.
Please see @ref{margin} for details.

@node trange, urange, tmargin, set-show
@subsection trange

@c ?commands set trange
@c ?commands show trange
@c ?set trange
@c ?show trange
@cindex trange
@opindex trange


The @ref{trange} command sets the parametric range used to compute x and y
values when in parametric or polar modes.  Please see @ref{xrange} for
details.

@node urange, variables, trange, set-show
@subsection urange

@c ?commands set urange
@c ?commands show urange
@c ?set urange
@c ?show urange
@cindex urange
@opindex urange


The @ref{urange} and @ref{vrange} commands set the parametric ranges used
to compute x, y, and z values when in `splot` parametric mode.
Please see @ref{xrange} for details.

@node variables, version, urange, set-show
@subsection variables

@c ?commands show variables
@c ?show variables
The @ref{variables} command lists all user-defined variables and their
values.

Syntax:
@example
      show variables @{all@}

@end example

With the optional keyword "all", also the @ref{variables} that
begin with `GPVAL_` are listed.


@node version, view, variables, set-show
@subsection version

@c ?show version
The @ref{version} command lists the version of gnuplot being run, its last
modification date, the copyright holders, and email addresses for the FAQ,
the gnuplot-info mailing list, and reporting bugs--in short, the information
listed on the screen when the program is invoked interactively.

Syntax:
@example
      show version @{long@}

@end example

When the `long` option is given, it also lists the operating system, the
compilation options used when `gnuplot` was installed, the location of the
help file, and (again) the useful email addresses.

@node view, vrange, version, set-show
@subsection view

@c ?commands set view
@c ?commands show view
@c ?set view
@c ?set view map
@c ?set view @{no@}equal @{xy|xyz@}
@c ?show view
@cindex view
@opindex view


The @ref{view} command sets the viewing angle for `splot`s.  It controls how
the 3-d coordinates of the plot are mapped into the 2-d screen space.  It
provides controls for both rotation and scaling of the plotted data, but
supports orthographic projections only.  It supports both 3D projection or
orthogonal 2D projection into a 2D plot-like map.

Syntax:
@example
      set view <rot_x>@{,@{<rot_z>@}@{,@{<scale>@}@{,<scale_z>@}@}@}
      set view map
      set view @{no@}equal_axes
      show view

@end example

where <rot_x> and <rot_z> control the rotation angles (in degrees) in a
virtual 3-d coordinate system aligned with the screen such that initially
(that is, before the rotations are performed) the screen horizontal axis is
x, screen vertical axis is y, and the axis perpendicular to the screen is z.
The first rotation applied is <rot_x> around the x axis.  The second rotation
applied is <rot_z> around the new z axis.

Command `set view map` is used to represent the drawing as a map. It can be
used for @ref{contour} plots, or for color @ref{pm3d} maps. In the latter, take care
that you properly use @ref{zrange} and @ref{cbrange} for input data point filtering
and color range scaling, respectively.

<rot_x> is bounded to the [0:180] range with a default of 60 degrees, while
<rot_z> is bounded to the [0:360] range with a default of 30 degrees.
<scale> controls the scaling of the entire `splot`, while <scale_z> scales
the z axis only.  Both scales default to 1.0.

Examples:
@example
      set view 60, 30, 1, 1
      set view ,,0.5

@end example

The first sets all the four default values.  The second changes only scale,
to 0.5.

The command `set view equal xy` forces the unit length of the x and y axes
to be on the same scale, and chooses that scale so that the plot will fit on
the page.  The command `set view equal xyz` additionally sets the z axis
scale to match the x and y axes; however there is no guarantee that the
current z axis range will fit within the plot boundary.
By default all three axes are scaled independently to fill the available area.

See also @ref{ticslevel}.

@node vrange, x2data, view, set-show
@subsection vrange

@c ?commands set vrange
@c ?commands show vrange
@c ?set vrange
@c ?show vrange
@cindex vrange
@opindex vrange


The @ref{urange} and @ref{vrange} commands set the parametric ranges used
to compute x, y, and z values when in `splot` parametric mode.
Please see @ref{xrange} for details.

@node x2data, x2dtics, vrange, set-show
@subsection x2data

@c ?commands set x2data
@c ?commands show x2data
@c ?set x2data
@c ?show x2data
@cindex x2data
@opindex x2data


The @ref{x2data} command sets data on the x2 (top) axis to timeseries
(dates/times).  Please see @ref{xdata}.

@node x2dtics, x2label, x2data, set-show
@subsection x2dtics

@c ?commands set x2dtics
@c ?commands unset x2dtics
@c ?commands show x2dtics
@c ?set x2dtics
@c ?unset x2dtics
@c ?show x2dtics
@cindex x2dtics
@opindex x2dtics


@cindex nox2dtics

The @ref{x2dtics} command changes tics on the x2 (top) axis to days of the
week.  Please see @ref{xdtics} for details.

@node x2label, x2mtics, x2dtics, set-show
@subsection x2label

@c ?commands set x2label
@c ?commands show x2label
@c ?set x2label
@c ?show x2label
@cindex x2label
@opindex x2label


The @ref{x2label} command sets the label for the x2 (top) axis.
Please see @ref{xlabel}.

@node x2mtics, x2range, x2label, set-show
@subsection x2mtics

@c ?commands set x2mtics
@c ?commands unset x2mtics
@c ?commands show x2mtics
@c ?set x2mtics
@c ?unset x2mtics
@c ?show x2mtics
@cindex x2mtics
@opindex x2mtics


@cindex nox2mtics

The @ref{x2mtics} command changes tics on the x2 (top) axis to months of the
year.  Please see @ref{xmtics} for details.

@node x2range, x2tics, x2mtics, set-show
@subsection x2range

@c ?commands set x2range
@c ?commands show x2range
@c ?set x2range
@c ?show x2range
@cindex x2range
@opindex x2range


The @ref{x2range} command sets the horizontal range that will be displayed on
the x2 (top) axis.  Please see @ref{xrange} for details.

@node x2tics, x2zeroaxis, x2range, set-show
@subsection x2tics

@c ?commands set x2tics
@c ?commands unset x2tics
@c ?commands show x2tics
@c ?set x2tics
@c ?unset x2tics
@c ?show x2tics
@cindex x2tics
@opindex x2tics


@cindex nox2tics

The @ref{x2tics} command controls major (labelled) tics on the x2 (top) axis.
Please see `set xtics` for details.

@node x2zeroaxis, xdata, x2tics, set-show
@subsection x2zeroaxis

@c ?commands set x2zeroaxis
@c ?commands unset x2zeroaxis
@c ?commands show x2zeroaxis
@c ?set x2zeroaxis
@c ?unset x2zeroaxis
@c ?show x2zeroaxis
@cindex x2zeroaxis
@opindex x2zeroaxis


@cindex nox2zeroaxis

The @ref{x2zeroaxis} command draws a line at the origin of the x2 (top) axis
(y2 = 0).  For details, please see @ref{zeroaxis}.

@node xdata, xdtics, x2zeroaxis, set-show
@subsection xdata

@c ?commands set xdata
@c ?commands show xdata
@c ?set xdata
@c ?show xdata
@cindex xdata
@opindex xdata


This command sets the datatype on the x axis to time/date.  A similar command
does the same thing for each of the other axes.

Syntax:
@example
      set xdata @{time@}
      show xdata

@end example

The same syntax applies to @ref{ydata}, @ref{zdata}, @ref{x2data}, @ref{y2data} and @ref{cbdata}.

The `time` option signals that the datatype is indeed time/date.  If the
option is not specified, the datatype reverts to normal.

See @ref{timefmt} to tell gnuplot how to read date or time data.  The
time/date is converted to seconds from start of the century.  There is
currently only one timefmt, which implies that all the time/date columns must
conform to this format.  Specification of ranges should be supplied as quoted
strings according to this format to avoid interpretation of the time/date as
an expression.

The function 'strftime' (type "man strftime" on unix to look it up) is used
to print tic-mark labels.  `gnuplot` tries to figure out a reasonable format
for this  unless the `set format x "string"` has supplied something that does
not look like a decimal format (more than one '%' or neither %f nor %g).

See also `Time/date` for more information.

@node xdtics, xlabel, xdata, set-show
@subsection xdtics

@c ?commands set xdtics
@c ?commands unset xdtics
@c ?commands show xdtics
@c ?set xdtics
@c ?unset xdtics
@c ?show xdtics
@cindex xdtics
@opindex xdtics


@cindex noxdtics

The @ref{xdtics} commands converts the x-axis tic marks to days of the week
where 0=Sun and 6=Sat.  Overflows are converted modulo 7 to dates.  `set
noxdtics` returns the labels to their default values.  Similar commands do
the same things for the other axes.

Syntax:
@example
      set xdtics
      unset xdtics
      show xdtics

@end example

The same syntax applies to @ref{ydtics}, @ref{zdtics}, @ref{x2dtics}, @ref{y2dtics} and
@ref{cbdtics}.

See also the `set format` command.

@node xlabel, xmtics, xdtics, set-show
@subsection xlabel

@c ?commands set xlabel
@c ?commands show xlabel
@c ?set xlabel
@c ?show xlabel
@cindex xlabel
@opindex xlabel


The @ref{xlabel} command sets the x axis label.  Similar commands set labels
on the other axes.

Syntax:
@example
      set xlabel @{"<label>"@} @{offset <offset>@} @{font "<font>@{,<size>@}"@}
                 @{@{textcolor | tc@} @{lt <line_type> | default@}@} @{@{no@}enhanced@}
                 @{rotate by <degrees>@}
      show xlabel

@end example

The same syntax applies to @ref{x2label}, @ref{ylabel}, @ref{y2label}, @ref{zlabel} and
@ref{cblabel}.

If <offset> is specified by either x,y or x,y,z the label is moved by the
given offset.  It may be preceded by `first`, `second`, `graph`, `screen`,
or `character` to select the coordinate system.  See `coordinates` for
details.  By default, the `character` coordinate system is used.  For
example, "`set xlabel offset -1,0`" will change only the x offset of the
title, moving the label roughly one character width to the left.  The size
of a character depends on both the font and the terminal.

<font> is used to specify the font in which the label is written; the units
of the font <size> depend upon which terminal is used.

`textcolor lt <n>` sets the text color to that of line type <n>.

`noenhanced` requests that the label text not be processed by the enhanced text
mode parser, even if enhanced text mode is currently active.

To clear a label, put no options on the command line, e.g., "@ref{y2label}".

The default positions of the axis labels are as follows:

xlabel:  The x-axis label is centered below the bottom axis.

ylabel:  The position of the y-axis label depends on the terminal, and can be
one of the following three positions:

1. Horizontal text flushed left at the top left of the plot.  Terminals that
cannot rotate text will probably use this method.  If @ref{x2tics} is also
in use, the ylabel may overwrite the left-most x2tic label.  This may be
remedied by adjusting the ylabel position or the left margin.

2. Vertical text centered vertically at the left of the plot.  Terminals
that can rotate text will probably use this method.

3. Horizontal text centered vertically at the left of the plot.  The EEPIC,
LaTeX and TPIC drivers use this method.  The EEPIC driver will produce a
stack of characters so as not to overwrite the plot. With other drivers
(such as LaTeX and TPIC), the user probably has to insert line breaks
using \\ to prevent the ylabel from overwriting the plot.

zlabel: The z-axis label is centered along the z axis and placed in the space
above the grid level.

cblabel: The color box axis label is centered along the box and placed below
or right according to horizontal or vertical color box gradient.

y2label: The y2-axis label is placed to the right of the y2 axis.  The
position is terminal-dependent in the same manner as is the y-axis label.

x2label: The x2-axis label is placed above the top axis but below the plot
title.  It is also possible to create an x2-axis label by using new-line
characters to make a multi-line plot title, e.g.,

@example
      set title "This is the title\n\nThis is the x2label"

@end example

Note that double quotes must be used.  The same font will be used for both
lines, of course.

The y and y2 axis labels can be explicitly rotated from their default
orientation, but this applies only to 2D plots and only on terminals
that support text rotation.

If you are not satisfied with the default position of an axis label, use @ref{label} instead--that command gives you much more control over where text is
placed.

Please see `syntax` for further information about backslash processing
and the difference between single- and double-quoted strings.

@node xmtics, xrange, xlabel, set-show
@subsection xmtics

@c ?commands set xmtics
@c ?commands unset xmtics
@c ?commands show xmtics
@c ?set xmtics
@c ?unset xmtics
@c ?show xmtics
@cindex xmtics
@opindex xmtics


@cindex noxmtics

The @ref{xmtics} command converts the x-axis tic marks to months of the
year where 1=Jan and 12=Dec.  Overflows are converted modulo 12 to months.
The tics are returned to their default labels by @ref{xmtics}.  Similar
commands perform the same duties for the other axes.

Syntax:
@example
      set xmtics
      unset xmtics
      show xmtics

@end example

The same syntax applies to @ref{x2mtics}, @ref{ymtics}, @ref{y2mtics}, @ref{zmtics} and
@ref{cbmtics}.

See also the `set format` command.

@node xrange, xtics, xmtics, set-show
@subsection xrange

@c ?commands set xrange
@c ?commands show xrange
@c ?set xrange
@c ?show xrange
@cindex writeback

@cindex restore

@cindex xrange
@opindex xrange


The @ref{xrange} command sets the horizontal range that will be displayed.
A similar command exists for each of the other axes, as well as for the
polar radius r and the parametric variables t, u, and v.

Syntax:
@example
      set xrange @{ [@{@{<min>@}:@{<max>@}@}] @{@{no@}reverse@} @{@{no@}writeback@} @}
                 | restore
      show xrange

@end example

where <min> and <max> terms are constants, expressions or an asterisk to set
autoscaling.  If the data are time/date, you must give the range as a quoted
string according to the @ref{timefmt} format.  Any value omitted will not be
changed.

The same syntax applies to @ref{yrange}, @ref{zrange}, @ref{x2range}, @ref{y2range}, @ref{cbrange},
@ref{rrange}, @ref{trange}, @ref{urange} and @ref{vrange}.

The `reverse` option reverses the direction of the axis, e.g., `set xrange
[0:1] reverse` will produce an axis with 1 on the left and 0 on the right.
This is identical to the axis produced by `set xrange [1:0]`, of course.
`reverse` is intended primarily for use with @ref{autoscale}.

The `writeback` option essentially saves the range found by @ref{autoscale} in
the buffers that would be filled by @ref{xrange}.  This is useful if you wish
to plot several functions together but have the range determined by only
some of them.  The `writeback` operation is performed during the `plot`
execution, so it must be specified before that command.  To restore,
the last saved horizontal range use `set xrange restore`.  For example,

@example
      set xrange [-10:10]
      set yrange [] writeback
      plot sin(x)
      set yrange restore
      replot x/2

@end example

results in a yrange of [-1:1] as found only from the range of sin(x); the
[-5:5] range of x/2 is ignored.  Executing @ref{yrange} after each command
in the above example should help you understand what is going on.

In 2-d, @ref{xrange} and @ref{yrange} determine the extent of the axes, @ref{trange}
determines the range of the parametric variable in parametric mode or the
range of the angle in polar mode.  Similarly in parametric 3-d, @ref{xrange},
@ref{yrange}, and @ref{zrange} govern the axes and @ref{urange} and @ref{vrange} govern the
parametric variables.

In polar mode, @ref{rrange} determines the radial range plotted.  <rmin> acts as
an additive constant to the radius, whereas <rmax> acts as a clip to the
radius---no point with radius greater than <rmax> will be plotted.  @ref{xrange}
and @ref{yrange} are affected---the ranges can be set as if the graph was of
r(t)-rmin, with rmin added to all the labels.

Any range may be partially or totally autoscaled, although it may not make
sense to autoscale a parametric variable unless it is plotted with data.

Ranges may also be specified on the `plot` command line.  A range given on
the plot line will be used for that single `plot` command; a range given by
a `set` command will be used for all subsequent plots that do not specify
their own ranges.  The same holds true for `splot`.

Examples:

To set the xrange to the default:
@example
      set xrange [-10:10]

@end example

To set the yrange to increase downwards:
@example
      set yrange [10:-10]

@end example

To change zmax to 10 without affecting zmin (which may still be autoscaled):
@example
      set zrange [:10]

@end example

To autoscale xmin while leaving xmax unchanged:
@example
      set xrange [*:]

@end example

@node xtics, xyplane, xrange, set-show
@subsection xtics

@c ?commands set xtics
@c ?commands unset xtics
@c ?commands show xtics
@c ?set xtics
@c ?unset xtics
@c ?show xtics
@cindex xtics
@opindex xtics


@cindex noxtics

Fine control of the major (labelled) tics on the x axis is possible with the
`set xtics` command.  The tics may be turned off with the `unset xtics`
command, and may be turned on (the default state) with `set xtics`.  Similar
commands control the major tics on the y, z, x2 and y2 axes.

Syntax:
@example
      set xtics @{axis | border@} @{@{no@}mirror@}
                @{in | out@} @{scale @{default | <major> @{,<minor>@}@}@}
                @{@{no@}rotate @{by <ang>@}@} @{offset <offset> | nooffset@}
                @{add@}
                @{  autofreq
                 | <incr>
                 | <start>, <incr> @{,<end>@}
                 | (@{"<label>"@} <pos> @{<level>@} @{,@{"<label>"@}...) @}
                @{ format "formatstring" @} @{ font "name@{,<size>@}" @}
                @{ rangelimited @}
                @{ textcolor <colorspec> @}
      unset xtics
      show xtics

@end example

The same syntax applies to @ref{ytics}, @ref{ztics}, @ref{x2tics}, @ref{y2tics} and @ref{cbtics}.

`axis` or @ref{border} tells `gnuplot` to put the tics (both the tics themselves
and the accompanying labels) along the axis or the border, respectively.  If
the axis is very close to the border, the `axis` option will move the
tic labels to outside the border.  The relevant margin settings will usually
be sized badly by the automatic layout algorithm in this case.

`mirror` tells `gnuplot` to put unlabelled tics at the same positions on the
opposite border.  `nomirror` does what you think it does.

`in` and `out` change the tic marks to be drawn inwards or outwards.

With `scale`, the size of the tic marks can be adjusted. If <minor> is not
specified, it is 0.5*<major>.  The default size 1.0 for major tics and 0.5
for minor tics is requested by `scale default`.

`rotate` asks `gnuplot` to rotate the text through 90 degrees, which will be
done if the terminal driver in use supports text rotation.  `norotate`
cancels this. `rotate by <ang>` asks for rotation by <ang> degrees, supported
by some terminal types.

The defaults are `border mirror norotate` for tics on the x and y axes, and
`border nomirror norotate` for tics on the x2 and y2 axes.  For the z axis,
the `@{axis | border@}` option is not available and the default is
`nomirror`.  If you do want to mirror the z-axis tics, you might want to
create a bit more room for them with @ref{border}.

The <offset> is specified by either x,y or x,y,z, and may be preceded by
`first`, `second`, `graph`, `screen`, or `character` to select the
coordinate system. <offset> is the offset of the tics texts from their
default positions, while the default coordinate system is `character`.
See `coordinates` for details. `nooffset` switches off the offset.

Example:

Move xtics more closely to the plot.
@example
      set xtics offset 0,graph 0.05

@end example

`set xtics` with no options restores the default border or axis if xtics are
being displayed;  otherwise it has no effect.  Any previously specified tic
frequency or position @{and labels@} are retained.

Positions of the tics are calculated automatically by default or if the
`autofreq` option is given; otherwise they may be specified in either of
two forms:

The implicit <start>, <incr>, <end> form specifies that a series of tics will
be plotted on the axis between the values <start> and <end> with an increment
of <incr>.  If <end> is not given, it is assumed to be infinity.  The
increment may be negative.  If neither <start> nor <end> is given, <start> is
assumed to be negative infinity, <end> is assumed to be positive infinity,
and the tics will be drawn at integral multiples of <incr>.  If the axis is
logarithmic, the increment will be used as a multiplicative factor.

If you specify to a negative <start> or <incr> after a numerical value
(e.g., `rotate by <angle>` or `offset <offset>`), the parser fails because
it subtracts <start> or <incr> from that value.  As a workaround, specify
`0-<start>` resp. `0-<incr>` in that case.

Example:
@example
      set xtics border offset 0,0.5 -5,1,5
@end example

Fails with 'invalid expression' at the last comma.
@example
      set xtics border offset 0,0.5 0-5,1,5
@end example

or
@example
      set xtics offset 0,0.5 border -5,1,5
@end example

Sets tics at the border, tics text with an offset of 0,0.5 characters, and
sets the start, increment, and end to -5, 1, and 5, as requested.

The `set grid` options 'front', 'back' and 'layerdefault' affect the drawing
order of the xtics, too.

Examples:

Make tics at 0, 0.5, 1, 1.5, ..., 9.5, 10.
@example
      set xtics 0,.5,10

@end example

Make tics at ..., -10, -5, 0, 5, 10, ...
@example
      set xtics 5

@end example

Make tics at 1, 100, 1e4, 1e6, 1e8.
@example
      set logscale x; set xtics 1,100,1e8

@end example

The explicit ("<label>" <pos> <level>, ...) form allows arbitrary tic
positions or non-numeric tic labels.  In this form, the tics do not
need to be listed in numerical order.  Each tic has a
position, optionally with a label.  Note that the label is
a string enclosed by quotes.  It may be a constant string, such as
"hello", may contain formatting information for converting the
position into its label, such as "%3f clients", or may be empty, "".
See `set format` for more information.  If no string is given, the
default label (numerical) is used.

An explicit tic mark has a third parameter, the "level".  The default
is level 0, a major tic.  A level of 1 generates a minor tic.  If the
level is specified, then the label must also be supplied.

Examples:
@example
      set xtics ("low" 0, "medium" 50, "high" 100)
      set xtics (1,2,4,8,16,32,64,128,256,512,1024)
      set ytics ("bottom" 0, "" 10, "top" 20)
      set ytics ("bottom" 0, "" 10 1, "top" 20)

@end example

In the second example, all tics are labelled.  In the third, only the end
tics are labelled.  In the fourth, the unlabeled tic is a minor tic.

Normally if explicit tics are given, they are used instead of auto-generated
tics. Conversely if you specify `set xtics auto` or the like it will erase
any previously specified explicit tics. You can mix explicit and auto-
generated tics by using the keyword `add`, which must appear before
the tic style being added.

Example:
@example
      set xtics 0,.5,10
      set xtics add ("Pi" 3.14159)

@end example

This will automatically generate tic marks every 0.5 along x, but will
also add an explicit labeled tic mark at pi.

However they are specified, tics will only be plotted when in range.

Format (or omission) of the tic labels is controlled by `set format`, unless
the explicit text of a label is included in the `set xtics ("<label>")` form.

Minor (unlabelled) tics can be added automatically by the @ref{mxtics}
command, or at explicit positions by the `set xtics ("" <pos> 1, ...)` form.

@menu
* xtics_time_data::             
* xtics_rangelimited::          
@end menu

@node xtics_time_data, xtics_rangelimited, xtics, xtics
@subsubsection xtics time_data

@c ?set xtics time_axis tics
@c ?xtics time_axis tics
@c ?time_axis tics
In case of timeseries data, axis tic position values must be given as quoted
dates or times according to the format @ref{timefmt}. If the <start>, <incr>, <end>
form is used, <start> and <end> must be given according to @ref{timefmt}, but
<incr> must be in seconds.  Times will be written out according to the format
given on `set format`, however.

Examples:
@example
      set xdata time
      set timefmt "%d/%m"
      set xtics format "%b %d"
      set xrange ["01/12":"06/12"]
      set xtics "01/12", 172800, "05/12"

@end example

@example
      set xdata time
      set timefmt "%d/%m"
      set xtics format "%b %d"
      set xrange ["01/12":"06/12"]
      set xtics ("01/12", "" "03/12", "05/12")
@end example

Both of these will produce tics "Dec 1", "Dec 3", and "Dec 5", but in the
second example the tic at "Dec 3" will be unlabelled.

@node xtics_rangelimited,  , xtics_time_data, xtics
@subsubsection xtics rangelimited

@c ?set xtics rangelimited
@c ?xtics rangelimited
@cindex rangelimited

@cindex range-frame

This option limits both the auto-generated axis tic labels and the
corresponding plot border to the range of values actually present in the data
that has been plotted.  Note that this is independent of the current range 
limits for the plot. For example, suppose that the data in "file.dat" all lies
in the range 2 < y < 4.  Then the following commands will create a plot for
which the left-hand plot border (y axis) is drawn for only this portion of the
total y range, and only the axis tics in this region are generated.
I.e., the plot will be scaled to the full range on y, but there will be a gap
between 0 and 2 on the left border and another gap between 4 and 10. This
style is sometimes refered to as a `range-frame` graph.
@example
      set border 3
      set yrange [0:10]
      set ytics nomirror rangelimited
      plot "file.dat"

@end example

@node xyplane, xzeroaxis, xtics, set-show
@subsection xyplane

@c ?commands set ticslevel
@c ?commands show ticslevel
@c ?set ticslevel
@c ?show ticslevel
@cindex ticslevel
@opindex ticslevel


@c ?commands set xyplane
@c ?commands show xyplane
@c ?set xyplane
@c ?show xyplane
@cindex xyplane
@opindex xyplane


The @ref{xyplane} command adjusts the position at which the xy plane is drawn
in a 3D plot.  The synonym "set ticslevel" is accepted for backwards
compatibility.

Syntax:
@example
      set ticslevel <frac>
      set xyplane <frac>
      set xyplane at <zvalue>
      show xyplane

@end example

The form `set ticslevel <frac>` places the xy plane below the range in Z, where
the distance from the xy plane to Zmin is given as a fraction of the total
range in z.  The default value is 0.5.  Negative values are permitted, but tic
labels on the three axes may overlap.

To place the xy-plane at a position 'pos' on the z-axis, @ref{ticslevel} may
be set equal to  (pos - zmin) / (zmin - zmax).  However, this position will
change if the z range is changed.

The alternative form `set xyplane at <zvalue>` fixes the placement of the
xy plane at a specific Z value regardless of the current z range. Thus to
force the x, y, and z axes to meet at a common origin one would specify
`set xyplane at 0`.

See also @ref{view}, and @ref{zeroaxis}.

@node xzeroaxis, y2data, xyplane, set-show
@subsection xzeroaxis

@c ?commands set xzeroaxis
@c ?commands unset xzeroaxis
@c ?commands show xzeroaxis
@c ?set xzeroaxis
@c ?unset xzeroaxis
@c ?show xzeroaxis
@cindex xzeroaxis
@opindex xzeroaxis


@cindex noxzeroaxis

The @ref{xzeroaxis} command draws a line at y = 0.  For details,
please see @ref{zeroaxis}.

@node y2data, y2dtics, xzeroaxis, set-show
@subsection y2data

@c ?commands set y2data
@c ?commands show y2data
@c ?set y2data
@c ?show y2data
@cindex y2data
@opindex y2data


The @ref{y2data} command sets y2 (right-hand) axis data to timeseries
(dates/times).  Please see @ref{xdata}.

@node y2dtics, y2label, y2data, set-show
@subsection y2dtics

@c ?commands set y2dtics
@c ?commands unset y2dtics
@c ?set y2dtics
@c ?unset y2dtics
@c ?show y2dtics
@cindex y2dtics
@opindex y2dtics


@cindex noy2dtics

The @ref{y2dtics} command changes tics on the y2 (right-hand) axis to days of
the week.  Please see @ref{xdtics} for details.

@node y2label, y2mtics, y2dtics, set-show
@subsection y2label

@c ?commands set y2label
@c ?commands show y2label
@c ?set y2label
@c ?show y2label
@cindex y2label
@opindex y2label


The @ref{y2label} command sets the label for the y2 (right-hand) axis.
Please see @ref{xlabel}.

@node y2mtics, y2range, y2label, set-show
@subsection y2mtics

@c ?commands set y2mtics
@c ?commands unset y2mtics
@c ?commands show y2mtics
@c ?set y2mtics
@c ?unset y2mtics
@c ?show y2mtics
@cindex y2mtics
@opindex y2mtics


@cindex noy2mtics

The @ref{y2mtics} command changes tics on the y2 (right-hand) axis to months
of the year.  Please see @ref{xmtics} for details.

@node y2range, y2tics, y2mtics, set-show
@subsection y2range

@c ?commands set y2range
@c ?commands show y2range
@c ?set y2range
@c ?show y2range
@cindex y2range
@opindex y2range


The @ref{y2range} command sets the vertical range that will be displayed on
the y2 (right-hand) axis.  Please see @ref{xrange} for details.

@node y2tics, y2zeroaxis, y2range, set-show
@subsection y2tics

@c ?commands set y2tics
@c ?commands unset y2tics
@c ?commands show y2tics
@c ?set y2tics
@c ?unset y2tics
@c ?show y2tics
@cindex y2tics
@opindex y2tics


@cindex noy2tics

The @ref{y2tics} command controls major (labelled) tics on the y2 (right-hand)
axis.  Please see `set xtics` for details.

@node y2zeroaxis, ydata, y2tics, set-show
@subsection y2zeroaxis

@c ?commands set y2zeroaxis
@c ?commands unset y2zeroaxis
@c ?commands show y2zeroaxis
@c ?set y2zeroaxis
@c ?unset y2zeroaxis
@c ?show y2zeroaxis
@cindex y2zeroaxis
@opindex y2zeroaxis


@cindex noy2zeroaxis

The @ref{y2zeroaxis} command draws a line at the origin of the y2 (right-hand)
axis (x2 = 0).  For details, please see @ref{zeroaxis}.

@node ydata, ydtics, y2zeroaxis, set-show
@subsection ydata

@c ?commands set ydata
@c ?commands show ydata
@c ?set ydata
@c ?show ydata
@cindex ydata
@opindex ydata


The @ref{ydata} commands sets y-axis data to timeseries (dates/times).
Please see @ref{xdata}.

@node ydtics, ylabel, ydata, set-show
@subsection ydtics

@c ?commands set ydtics
@c ?commands unset ydtics
@c ?commands show ydtics
@c ?set ydtics
@c ?unset ydtics
@c ?show ydtics
@cindex ydtics
@opindex ydtics


@cindex noydtics

The @ref{ydtics} command changes tics on the y axis to days of the week.
Please see @ref{xdtics} for details.

@node ylabel, ymtics, ydtics, set-show
@subsection ylabel

@c ?commands set ylabel
@c ?commands show ylabel
@c ?set ylabel
@c ?show ylabel
@cindex ylabel
@opindex ylabel


This command sets the label for the y axis.  Please see @ref{xlabel}.

@node ymtics, yrange, ylabel, set-show
@subsection ymtics

@c ?commands set ymtics
@c ?commands unset ymtics
@c ?commands show ymtics
@c ?set ymtics
@c ?unset ymtics
@c ?show ymtics
@cindex ymtics
@opindex ymtics


@cindex noymtics

The @ref{ymtics} command changes tics on the y axis to months of the year.
Please see @ref{xmtics} for details.

@node yrange, ytics, ymtics, set-show
@subsection yrange

@c ?commands set yrange
@c ?commands show yrange
@c ?set yrange
@c ?show yrange
@cindex yrange
@opindex yrange


The @ref{yrange} command sets the vertical range that will be displayed on
the y axis.  Please see @ref{xrange} for details.

@node ytics, yzeroaxis, yrange, set-show
@subsection ytics

@c ?commands set ytics
@c ?commands unset ytics
@c ?commands show ytics
@c ?set ytics
@c ?unset ytics
@c ?show ytics
@cindex ytics
@opindex ytics


@cindex noytics

The @ref{ytics} command controls major (labelled) tics on the y axis.
Please see `set xtics` for details.

@node yzeroaxis, zdata, ytics, set-show
@subsection yzeroaxis

@c ?commands set yzeroaxis
@c ?commands unset yzeroaxis
@c ?commands show yzeroaxis
@c ?set yzeroaxis
@c ?unset yzeroaxis
@c ?show yzeroaxis
@cindex yzeroaxis
@opindex yzeroaxis


@cindex noyzeroaxis

The @ref{yzeroaxis} command draws a line at x = 0.  For details,
please see @ref{zeroaxis}.

@node zdata, zdtics, yzeroaxis, set-show
@subsection zdata

@c ?commands set zdata
@c ?commands show zdata
@c ?set zdata
@c ?show zdata
@cindex zdata
@opindex zdata


The @ref{zdata} command sets zaxis data to timeseries (dates/times).
Please see @ref{xdata}.

@node zdtics, zzeroaxis, zdata, set-show
@subsection zdtics

@c ?commands set zdtics
@c ?commands unset zdtics
@c ?commands show zdtics
@c ?set zdtics
@c ?unset zdtics
@c ?show zdtics
@cindex zdtics
@opindex zdtics


@cindex nozdtics

The @ref{zdtics} command changes tics on the z axis to days of the week.
Please see @ref{xdtics} for details.

@node zzeroaxis, cbdata, zdtics, set-show
@subsection zzeroaxis

@c ?commands set zzeroaxis
@c ?commands unset zzeroaxis
@c ?commands show zzeroaxis
@c ?set zzeroaxis
@c ?unset zzeroaxis
@c ?show zzeroaxis
@cindex zzeroaxis
@opindex zzeroaxis


@cindex nozzeroaxis

The @ref{zzeroaxis} command draws a line through (x=0,y=0).  This has no effect
on 2D plots, including splot with `set view map`. For details, please
see @ref{zeroaxis} and @ref{xyplane}.

@node cbdata, cbdtics, zzeroaxis, set-show
@subsection cbdata

@c ?commands set cbdata
@c ?commands show cbdata
@c ?set cbdata
@c ?show cbdata
@cindex cbdata
@opindex cbdata


Set color box axis data to timeseries (dates/times).  Please see @ref{xdata}.

@node cbdtics, zero, cbdata, set-show
@subsection cbdtics

@c ?commands set cbdtics
@c ?commands unset cbdtics
@c ?commands show cbdtics
@c ?set cbdtics
@c ?unset cbdtics
@c ?show cbdtics
@cindex cbdtics
@opindex cbdtics


@cindex nocbdtics

The @ref{cbdtics} command changes tics on the color box axis to days of the
week. Please see @ref{xdtics} for details.

@node zero, zeroaxis, cbdtics, set-show
@subsection zero

@c ?commands set zero
@c ?commands show zero
@c ?set zero
@c ?show zero
@cindex zero
@opindex zero


The `zero` value is the default threshold for values approaching 0.0.

Syntax:
@example
      set zero <expression>
      show zero

@end example

`gnuplot` will not plot a point if its imaginary part is greater in magnitude
than the `zero` threshold.  This threshold is also used in various other
parts of `gnuplot` as a (crude) numerical-error threshold.  The default
`zero` value is 1e-8.  `zero` values larger than 1e-3 (the reciprocal of the
number of pixels in a typical bitmap display) should probably be avoided, but
it is not unreasonable to set `zero` to 0.0.

@node zeroaxis, zlabel, zero, set-show
@subsection zeroaxis

@c ?commands set zeroaxis
@c ?commands unset zeroaxis
@c ?commands show zeroaxis
@c ?set zeroaxis
@c ?unset zeroaxis
@c ?show zeroaxis
@cindex zeroaxis
@opindex zeroaxis


The x axis may be drawn by @ref{xzeroaxis} and removed by @ref{xzeroaxis}.
Similar commands behave similarly for the y, x2, y2, and z axes.

Syntax:
@example
      set @{x|x2|y|y2|z@}zeroaxis @{ @{linestyle | ls <line_style>@}
                                 | @{ linetype | lt <line_type>@}
                                   @{ linewidth | lw <line_width>@}@}
      unset @{x|x2|y|y2|z@}zeroaxis
      show @{x|y|z@}zeroaxis

@end example


By default, these options are off.  The selected zero axis is drawn
with a line of type <line_type> and width <line_width> (if supported
by the terminal driver currently in use), or a user-defined style
<line_style>.

If no linetype is specified, any zero axes selected will be drawn
using the axis linetype (linetype 0).

@ref{zeroaxis} is equivalent to @ref{yzeroaxis}.
Note that the z-axis must be set separately using @ref{zzeroaxis}.

Examples:

To simply have the y=0 axis drawn visibly:

@example
       set xzeroaxis

@end example

If you want a thick line in a different color or pattern, instead:

@example
       set xzeroaxis linetype 3 linewidth 2.5

@end example

@node zlabel, zmtics, zeroaxis, set-show
@subsection zlabel

@c ?commands set zlabel
@c ?commands show zlabel
@c ?set zlabel
@c ?show zlabel
@cindex zlabel
@opindex zlabel


This command sets the label for the z axis.  Please see @ref{xlabel}.

@node zmtics, zrange, zlabel, set-show
@subsection zmtics

@c ?commands set zmtics
@c ?commands unset zmtics
@c ?commands show zmtics
@c ?set zmtics
@c ?unset zmtics
@c ?show zmtics
@cindex zmtics
@opindex zmtics


@cindex nozmtics

The @ref{zmtics} command changes tics on the z axis to months of the year.
Please see @ref{xmtics} for details.

@node zrange, ztics, zmtics, set-show
@subsection zrange

@c ?commands set zrange
@c ?commands show zrange
@c ?set zrange
@c ?show zrange
@cindex zrange
@opindex zrange


The @ref{zrange} command sets the range that will be displayed on the z axis.
The zrange is used only by `splot` and is ignored by `plot`.  Please see
@ref{xrange} for details.

@node ztics, cblabel, zrange, set-show
@subsection ztics

@c ?commands set ztics
@c ?commands unset ztics
@c ?commands show ztics
@c ?set ztics
@c ?unset ztics
@c ?show ztics
@cindex ztics
@opindex ztics


@cindex noztics

The @ref{ztics} command controls major (labelled) tics on the z axis.
Please see `set xtics` for details.

@node cblabel, cbmtics, ztics, set-show
@subsection cblabel

@c ?commands set cblabel
@c ?commands show cblabel
@c ?set cblabel
@c ?show cblabel
@cindex cblabel
@opindex cblabel


This command sets the label for the color box axis.  Please see @ref{xlabel}.

@node cbmtics, cbrange, cblabel, set-show
@subsection cbmtics

@c ?commands set cbmtics
@c ?commands unset cbmtics
@c ?commands show cbmtics
@c ?set cbmtics
@c ?unset cbmtics
@c ?show cbmtics
@cindex cbmtics
@opindex cbmtics


@cindex nocbmtics

The @ref{cbmtics} command changes tics on the color box axis to months of the
year. Please see @ref{xmtics} for details.

@node cbrange, cbtics, cbmtics, set-show
@subsection cbrange

@c ?commands set cbrange
@c ?commands show cbrange
@c ?set cbrange
@c ?show cbrange
@cindex cbrange
@opindex cbrange


The @ref{cbrange} command sets the range of values which are colored using
the current @ref{palette} by styles @ref{pm3d}, `with image` and @ref{palette}.
Values outside of the color range use color of the nearest extreme.

If the cb-axis is autoscaled in `splot`, then the colorbox range is taken from
@ref{zrange}.  Points drawn in `splot ... pm3d|palette` can be filtered by using
different @ref{zrange} and @ref{cbrange}.

Please see @ref{xrange} for details on @ref{cbrange} syntax. See also
@ref{palette} and `set colorbox`.

@node cbtics,  , cbrange, set-show
@subsection cbtics

@c ?commands set cbtics
@c ?commands unset cbtics
@c ?commands show cbtics
@c ?set cbtics
@c ?unset cbtics
@c ?show cbtics
@cindex cbtics
@opindex cbtics


@cindex nocbtics

The @ref{cbtics} command controls major (labelled) tics on the color box axis.
Please see `set xtics` for details.

@node shell, splot, set-show, Commands
@section shell

@c ?commands shell
@cindex shell
@cmindex shell


The @ref{shell} command spawns an interactive shell.  To return to `gnuplot`,
type `logout` if using VMS, @ref{exit} or the END-OF-FILE character if using
Unix, `endcli` if using AmigaOS, or @ref{exit} if using MS-DOS or OS/2.

There are two ways of spawning a shell command: using @ref{system} command
or via `!` ($ if using VMS). The former command takes a string as a
parameter and thus it can be used anywhere among other gnuplot commands,
while the latter syntax requires to be the only command on the line. Control
will return immediately to `gnuplot` after this command is executed.  For
example, in AmigaOS, MS-DOS or OS/2,

@example
      ! dir
@end example

or
@example
      system "dir"

@end example


prints a directory listing and then returns to `gnuplot`.


Other examples of the former syntax:
@example
       system "date"; set time; plot "a.dat"
       print=1; if (print) replot; set out; system "lpr x.ps"

@end example

On an Atari, the `!` command first checks whether a shell is already loaded
and uses it, if available.  This is practical if `gnuplot` is run from
`gulam`, for example.

@node splot, system_, shell, Commands
@section splot

@c ?commands splot
@cindex splot
@cmindex splot


`splot` is the command for drawing 3-d plots (well, actually projections on
a 2-d surface, but you knew that).  It can create a plot from functions or
a data file in a manner very similar to the `plot` command.

See `plot` for features common to the `plot` command; only differences are
discussed in detail here.  Note specifically `plot`'s `axes` option is not
available for `splot`.

Syntax:
@example
      splot @{<ranges>@}
            <function> | "<datafile>" @{datafile-modifiers@}@}
            @{<title-spec>@} @{with <style>@}
            @{, @{definitions,@} <function> ...@}

@end example

where either a <function> or the name of a data file enclosed in quotes is
supplied.  The function can be a mathematical expression, or a triple of
mathematical expressions in parametric mode.

By default `splot` draws the xy plane completely below the plotted data.
The offset between the lowest ztic and the xy plane can be changed by @ref{ticslevel}.  The orientation of a `splot` projection is controlled by
@ref{view}.  See @ref{view} and @ref{ticslevel} for more information.

The syntax for setting ranges on the `splot` command is the same as for
`plot`.  In non-parametric mode, the order in which ranges must be given is
@ref{xrange}, @ref{yrange}, and @ref{zrange}.  In parametric mode, the order is @ref{urange},
@ref{vrange}, @ref{xrange}, @ref{yrange}, and @ref{zrange}.

The @ref{title} option is the same as in `plot`.  The operation of @ref{with} is also
the same as in `plot`, except that the plotting styles available to `splot`
are limited to `lines`, `points`, `linespoints`, `dots`, and `impulses`;  the
error-bar capabilities of `plot` are not available for `splot`.

The @ref{datafile} options have more differences.

See also `show plot`.

@menu
* data-file::                   
* grid_data::                   
* splot_overview::              
@end menu

@node data-file, grid_data, splot, splot
@subsection data-file

@c ?commands splot datafile
@c ?splot datafile
@c ?splot data-file
As for `plot`, discrete data contained in a file can be displayed by
specifying the name of the data file, enclosed in quotes,  on the `splot`
command line.

Syntax:
@example
      splot '<file_name>' @{binary <binary list>@}
                          @{matrix@}
                          @{index <index list>@}
                          @{every <every list>@}
                          @{using <using list>@}

@end example

The special filenames `""` and `"-"` are permitted, as in `plot`.

In brief, `binary` and `matrix` indicate that the data are in a special
form, @ref{index} selects which data sets in a multi-data-set file are to be
plotted, @ref{every} specifies which datalines (subsets) within a single data
set are to be plotted, and @ref{using} determines how the columns within a single
record are to be interpreted.

The options @ref{index} and @ref{every} behave the same way as with `plot`;  @ref{using}
does so also, except that the @ref{using} list must provide three entries
instead of two.

The `plot` options @ref{thru} and @ref{smooth} are not available for `splot`, but
@ref{cntrparam} and @ref{dgrid3d} provide limited smoothing capabilities.

Data file organization is essentially the same as for `plot`, except that
each point is an (x,y,z) triple.  If only a single value is provided, it
will be used for z, the datablock number will be used for y, and the index
of the data point in the datablock will be used for x.  If two or four values
are provided, `gnuplot` uses the last value for calculating the color in
pm3d plots.  Three values are interpreted as an (x,y,z) triple.  Additional
values are generally used as errors, which can be used by @ref{fit}.

Single blank records separate datablocks in a `splot` datafile; `splot`
treats datablocks as the equivalent of function y-isolines.  No line will
join points separated by a blank record.  If all datablocks contain the same
number of points, `gnuplot` will draw cross-isolines between datablocks,
connecting corresponding points.  This is termed "grid data", and is required
for drawing a surface, for contouring (@ref{contour}) and hidden-line removal
(@ref{hidden3d}). See also `splot grid_data`.

It is no longer necessary to specify `parametric` mode for three-column
`splot`s.

@menu
* binary_matrix::               
* example_datafile_::           
* matrix_ascii::                
* matrix::                      
@end menu

@node binary_matrix, example_datafile_, data-file, data-file
@subsubsection binary matrix

@c ?commands plot datafile binary matrix
@c ?commands splot datafile binary matrix
@c ?plot datafile matrix binary
@c ?splot datafile matrix binary
@c ?plot binary matrix
@c ?splot binary matrix
@c ?plot matrix binary
@c ?splot matrix binary
@c ?matrix binary
@c ?binary matrix
@cindex gpbin

Gnuplot can read matrix binary files by use of the option `binary` appearing
without keyword qualifications unique to general binary, i.e., `array`,
`record`, `format`, or `filetype`.  Other general binary keywords for
translation should also apply to matrix binary.  (See `binary general` for
more details.)

In previous versions, `gnuplot` dynamically detected binary data files.  It
is now necessary to specify the keyword `binary` directly after the filename.

Single precision floats are stored in a binary file as follows:

@example
      <N+1>  <y0>   <y1>   <y2>  ...  <yN>
       <x0> <z0,0> <z0,1> <z0,2> ... <z0,N>
       <x1> <z1,0> <z1,1> <z1,2> ... <z1,N>
        :      :      :      :   ...    :

@end example

which are converted into triplets:
@example
      <x0> <y0> <z0,0>
      <x0> <y1> <z0,1>
      <x0> <y2> <z0,2>
       :    :     :
      <x0> <yN> <z0,N>

@end example

@example
      <x1> <y0> <z1,0>
      <x1> <y1> <z1,1>
       :    :     :

@end example

These triplets are then converted into `gnuplot` iso-curves and then
`gnuplot` proceeds in the usual manner to do the rest of the plotting.

A collection of matrix and vector manipulation routines (in C) is provided
in `binary.c`.  The routine to write binary data is

@example
      int fwrite_matrix(file,m,nrl,nrl,ncl,nch,row_title,column_title)

@end example

An example of using these routines is provided in the file `bf_test.c`, which
generates binary files for the demo file `demo/binary.dem`.

The @ref{index} keyword is not supported, since the file format allows only one
surface per file.  The @ref{every} and @ref{using} filters are supported.  @ref{using}
operates as if the data were read in the above triplet form.

See also `binary general` and

@uref{http://www.gnuplot.info/demo/binary.html,Binary File Splot Demo.
}

@node example_datafile_, matrix_ascii, binary_matrix, data-file
@subsubsection example datafile

@c ?commands splot datafile example
@c ?splot datafile example
@c ?splot example
A simple example of plotting a 3-d data file is

@example
      splot 'datafile.dat'

@end example

where the file "datafile.dat" might contain:

@example
      # The valley of the Gnu.
         0 0 10
         0 1 10
         0 2 10

@end example

@example
         1 0 10
         1 1 5
         1 2 10

@end example

@example
         2 0 10
         2 1 1
         2 2 10

@end example

@example
         3 0 10
         3 1 0
         3 2 10

@end example

Note that "datafile.dat" defines a 4 by 3 grid ( 4 rows of 3 points each ).
Rows (datablocks) are separated by blank records.

@c ^ <img align=bottom src="http://www.gnuplot.info/doc/splot.gif" alt="[splot.gif]" width=640 height=480>
Note also that the x value is held constant within each dataline.  If you
instead keep y constant, and plot with hidden-line removal enabled, you will
find that the surface is drawn 'inside-out'.

Actually for grid data it is not necessary to keep the x values constant
within a datablock, nor is it necessary to keep the same sequence of y
values.  `gnuplot` requires only that the number of points be the same for
each datablock.  However since the surface mesh, from which contours are
derived, connects sequentially corresponding points, the effect of an
irregular grid on a surface plot is unpredictable and should be examined
on a case-by-case basis.

@node matrix_ascii, matrix, example_datafile_, data-file
@subsubsection matrix_ascii

@c ?commands plot datafile matrix ascii
@c ?commands splot datafile matrix ascii
@c ?plot datafile matrix ascii
@c ?splot datafile matrix ascii
@c ?plot matrix ascii
@c ?splot matrix ascii
@c ?data-file matrix ascii
@c ?datafile matrix ascii
@c ?matrix ascii
The `matrix` keyword (without a sequent `binary` keyword) in
@example
    @{s@}plot 'a.dat' matrix
@end example

indicates that data are stored in an ascii numbers matrix format.

The z-values are read in a row at a time, i. e.,
@example
    z11 z12 z13 z14 ...
    z21 z22 z23 z24 ...
    z31 z32 z33 z34 ...
@end example

and so forth.

In 3D, the x- and y-indices of the matrix surface plot correspond to column
and row indices of the matrix, respectively, being enumerated from 0. You can
rescale or transform the axes as usual for a data file with three columns
by means of x=$1, y=$2, z=$3. For example
@example
    splot 'a.dat' matrix using (1+$1/100):(1+$2*10):3

@end example

A blank line or comment line ends the matrix, and starts a new surface mesh.
You can select among the meshes inside a file by the @ref{index} option to the
`splot` command, as usual.

See `matrix` for examples of plotting rows and columns of the matrix in
a 2D plot.

@node matrix,  , matrix_ascii, data-file
@subsubsection matrix

@c ?commands plot datafile matrix
@c ?commands splot datafile matrix
@c ?plot datafile matrix
@c ?splot datafile matrix
@c ?plot matrix
@c ?splot matrix
@c ?data-file matrix
@c ?datafile matrix
@cindex matrix

Datafile can be in an ascii or binary matrix format. The `matrix` flag
indicates that the file is ascii, the `binary` or `matrix binary` stands for
a binary format. For details, see `matrix ascii` and `matrix binary`.

Basic usage in `splot`:
@example
    splot 'a.dat' matrix
    splot 'a.gpbin' @{matrix@} binary
@end example

Advanced usage in `splot`:
@example
    splot 'a.dat' matrix using 1:2:3
    splot 'a.gpbin' @{matrix@} binary using 1:2:3
@end example

allows to transform the axes coordinates and the z-data independently.

Usage in `plot`:
@example
    plot `a.dat` matrix
    plot `a.dat` matrix using 1:3
    plot 'a.gpbin' @{matrix@} binary using 1:3
@end example

will plot rows of the matrix, while using 2:3 will plot matrix columns, and
using 1:2 the point coordinates (rather useless). Applying the @ref{every} option
you can specify explicit rows and columns.

Example -- rescale axes of a matrix in an ascii file:
@example
    splot `a.dat` matrix using (1+$1):(1+$2*10):3

@end example

Example -- plot the 3rd row of a matrix in an ascii file:
@example
    plot 'a.dat' matrix using 1:3 every 1:999:1:2
@end example

(rows are enumerated from 0, thus 2 instead of 3).

@node grid_data, splot_overview, data-file, splot
@subsection grid data

@c ?commands splot grid_data
@c ?splot grid_data
@cindex grid_data

The 3D routines are designed for points in a grid format, with one sample,
datapoint, at each mesh intersection; the datapoints may originate from
either evaluating a function, see @ref{isosamples}, or reading a datafile,
see @ref{datafile}.  The term "isoline" is applied to the mesh lines for
both functions and data.  Note that the mesh need not be rectangular in x
and y, as it may be parameterized in u and v, see @ref{isosamples}.

However, `gnuplot` does not require that format.  In the case of functions,
'samples' need not be equal to 'isosamples', i.e., not every x-isoline
sample need intersect a y-isoline. In the case of data files, if there
are an equal number of scattered data points in each datablock, then
"isolines" will connect the points in a datablock, and "cross-isolines"
will connect the corresponding points in each datablock to generate a
"surface".  In either case, contour and hidden3d modes may give different
plots than if the points were in the intended format.  Scattered data can be
converted to a @{different@} grid format with @ref{dgrid3d}.

The contour code tests for z intensity along a line between a point on a
y-isoline and the corresponding point in the next y-isoline.  Thus a `splot`
contour of a surface with samples on the x-isolines that do not coincide with
a y-isoline intersection will ignore such samples. Try:
@example
       set xrange [-pi/2:pi/2]; set yrange [-pi/2:pi/2]
       set style function lp
       set contour
       set isosamples 10,10; set samples 10,10;
       splot cos(x)*cos(y)
       set samples 4,10; replot
       set samples 10,4; replot

@end example


@node splot_overview,  , grid_data, splot
@subsection splot overview

@c ?commands splot overview
@c ?splot overview
`splot` can display a surface as a collection of points, or by connecting
those points.  As with `plot`, the points may be read from a data file or
result from evaluation of a function at specified intervals, see
@ref{isosamples}.  The surface may be approximated by connecting the points
with straight line segments, see @ref{surface}, in which case the surface
can be made opaque with `set hidden3d.`  The orientation from which the 3d
surface is viewed can be changed with @ref{view}.

Additionally, for points in a grid format, `splot` can interpolate points
having a common amplitude (see @ref{contour}) and can then connect those
new points to display contour lines, either directly with straight-line
segments or smoothed lines (see @ref{cntrparam}).  Functions are already
evaluated in a grid format, determined by @ref{isosamples} and @ref{samples},
while file data must either be in a grid format, as described in @ref{data-file},
or be used to generate a grid (see @ref{dgrid3d}).

Contour lines may be displayed either on the surface or projected onto the
base.  The base projections of the contour lines may be written to a
file, and then read with `plot`, to take advantage of `plot`'s additional
formatting capabilities.

@node system_, test, splot, Commands
@section system

@c ?commands system
@cindex system
@cmindex system


`system "command"` executes "command" using the standard shell. See @ref{shell}.
If called as a function, `system("command")` returns the resulting character
stream from stdout as a string.  One optional trailing newline is ignored.

This can be used to import external functions into gnuplot scripts:

@example
      f(x) = real(system(sprintf("somecommand %f", x)))

@end example

@node test, undefine, system_, Commands
@section test

@c ?commands test
@c ?test palette
@cindex test
@cmindex test


This command graphically tests or presents terminal and palette capabilities.

Syntax:
@example
      test @{terminal | palette [rgb|rbg|grb|gbr|brg|bgr]@}

@end example

@ref{test} or @ref{terminal} creates a display of line and point styles and other
useful things appropriate for and supported by the @ref{terminal} you are just
using.

@ref{palette} draws graphically profiles R(z),G(z),B(z), where 0<=z<=1, as
calculated by the current color @ref{palette}. In other words, it is a beautiful
plot you would have to do yourself with the result of `show palette palette 256 float`.
The optional parameter, a permutation of letters rgb, determines the sequence of
r,g,b profiles drawn one after the other --- try this yourself for `set palette
gray`. The default sequence is rgb.

@node undefine, unset, test, Commands
@section undefine

@c ?commands undefine
@cindex undefine
@cmindex undefine


Clear one or more previously defined user variables.  This is useful in order
to reset the state of a script containing an initialization test.

Example:

@example
      undefine foo foo1 foo2
      if (!exists("foo")) load "initialize.gp"

@end example


@node unset, update, undefine, Commands
@section unset

@c ?commands unset
@cindex unset
@cmindex unset


Options set using the `set` command may be returned to their default state by
issuing the corresponding @ref{unset} command.

Example:
@example
      set xtics mirror rotate by -45 0,10,100
      ...
      unset xtics

@end example


@node update,  , unset, Commands
@section update

@c ?commands update
@cindex update
@cmindex update


This command writes the current values of the fit parameters into the given
file, formatted as an initial-value file (as described in the @ref{fit}section).
This is useful for saving the current values for later use or for restarting
a converged or stopped fit.

Syntax:
@example
      update <filename> @{<filename>@}

@end example

If a second filename is supplied, the updated values are written to this
file, and the original parameter file is left unmodified.

Otherwise, if the file already exists, `gnuplot` first renames it by
appending `.old` and then opens a new file.  That is, "`update 'fred'`"
behaves the same as "`!rename fred fred.old; update 'fred.old' 'fred'`".
[On DOS and other systems that use the twelve-character "filename.ext"
naming convention, "ext" will be "`old`" and "filename" will be related
(hopefully recognizably) to the initial name.  Renaming is not done at all
on VMS systems, since they use file-versioning.]

Please see @ref{fit} for more information.

@node Terminal_types, Graphical_User_Interfaces, Commands, Top
@chapter Terminal types

@c ^ <h2> Terminal Types </h2>

@menu
* terminal_::                   
@end menu

@node terminal_,  , Terminal_types, Terminal_types
@section terminal

@cindex terminal
@opindex terminal


@cindex term

Gnuplot supports a large number of output formats. These are selected by
choosing an appropriate terminal type, possibly with additional modifying
options. See @ref{terminal}.

This document may describe terminal types that are not available to you
because they were not configured or installed on your system. To see a list of
terminals available on a particular gnuplot installation, type 'set terminal'
with no modifiers.
@@c <3 -- all terminal stuff is pulled from the .trm files

@menu
* aed767::                      
* aifm::                        
* amiga::                       
* apollo::                      
* aqua::                        
* atari_ST_(via_AES)::          
* atari_ST_(via_VDI)::          
* be::                          
* cgi::                         
* cgm::                         
* corel::                       
* debug::                       
* svga::                        
* dumb::                        
* dxf::                         
* dxy800a::                     
* eepic::                       
* emf::                         
* emxvga::                      
* epson-180dpi::                
* excl::                        
* hercules::                    
* fig::                         
* png::                         
* ggi::                         
* Gnugraph(GNU_plotutils)::     
* gpic::                        
* gpic_::                       
* gpr::                         
* grass::                       
* hp2623a::                     
* hp2648::                      
* hp500c::                      
* hpgl::                        
* hpljii::                      
* hppj::                        
* imagen::                      
* iris4d::                      
* kyo::                         
* latex::                       
* linux::                       
* linux_::                      
* macintosh::                   
* mf::                          
* mp::                          
* mgr::                         
* mif::                         
* mtos::                        
* next::                        
* Openstep_(next)::             
* pbm::                         
* dospc::                       
* pdf::                         
* pstricks::                    
* qms::                         
* regis::                       
* regis_::                      
* rgip::                        
* sun::                         
* svg::                         
* tek410x::                     
* tek410x_::                    
* tek40::                       
* texdraw::                     
* tgif::                        
* tgif_::                       
* tkcanvas::                    
* tpic::                        
* unixpc::                      
* unixplot::                    
* vx384::                       
* vgagl::                       
* VWS::                         
* windows::                     
* x11::                         
* x11_::                        
* xlib::                        
* xlib_::                       
@end menu

@node aed767, aifm, terminal_, terminal_
@subsubsection aed767

@c ?commands set terminal aed767
@c ?set terminal aed767
@c ?set term aed767
@c ?terminal aed767
@c ?term aed767
@cindex aed767
@tmindex aed767


@c ?commands set terminal aed512
@c ?set terminal aed512
@c ?set term aed512
@c ?terminal aed512
@c ?term aed512
@cindex aed512
@tmindex aed512


The `aed512` and `aed767` terminal drivers support AED graphics terminals.
The two drivers differ only in their horizontal ranges, which are 512 and
768 pixels, respectively.  Their vertical range is 575 pixels.  There are
no options for these drivers."

@node aifm, amiga, aed767, terminal_
@subsubsection aifm

@c ?commands set terminal aifm
@c ?set terminal aifm
@c ?set term aifm
@c ?terminal aifm
@c ?term aifm
@cindex aifm


NOTE: this terminal driver is outdated. Since Adobe Illustrator understands
PostScript level 1 directly, you should use `set terminal post level1`
instead.

Several options may be set in `aifm`---the Adobe Illustrator 3.0+ driver.

Syntax:
@example
      set terminal aifm @{<color>@} @{"<fontname>"@} @{<fontsize>@}

@end example

<color> is either `color` or `monochrome`; "<fontname>" is the name of a
valid PostScript font; <fontsize> is the size of the font in PostScript
points, before scaling by the @ref{size} command.  Selecting `default` sets
all options to their default values: `monochrome`, "Times-Roman", and 14pt.

Since AI does not really support multiple pages, multiple graphs will be
drawn directly on top of one another.  However, each graph will be grouped
individually, making it easy to separate them inside AI (just pick them up
and move them).

Examples:
@example
      set term aifm
      set term aifm 22
      set size 0.7,1.4; set term aifm color "Times-Roman" 14"

@end example

@node amiga, apollo, aifm, terminal_
@subsubsection amiga

@c ?commands set terminal amiga
@c ?set terminal amiga
@c ?set term amiga
@c ?terminal amiga
@c ?term amiga
@cindex amiga
@tmindex amiga


The `amiga` terminal, for Commodore Amiga computers, allows the user to
plot either to a screen (default), or, if Kickstart 3.0 or higher is
installed, to a window on the current public screen. The font and its size
can also be selected.

Syntax:
@example
      set terminal amiga @{screen | window@} @{"<fontname>"@} @{<fontsize>@}

@end example

The default font is 8-point "topaz".

The screen option uses a virtual screen, so it is possible that the graph
will be larger than the screen."

@node apollo, aqua, amiga, terminal_
@subsubsection apollo

@c ?commands set terminal apollo
@c ?set terminal apollo
@c ?set term apollo
@c ?terminal apollo
@c ?term apollo
@cindex apollo
@tmindex apollo


The `apollo` terminal driver supports the Apollo Graphics Primitive Resource
with rescaling after window resizing.  It has no options.

If a fixed-size window is desired, the `gpr` terminal may be used instead."

@node aqua, atari_ST_(via_AES), apollo, terminal_
@subsubsection aqua

@c ?commands set terminal aqua
@c ?set terminal aqua
@c ?set term aqua
@c ?terminal aqua
@c ?term aqua
@cindex aqua

@cindex Aqua

This terminal relies on AquaTerm.app for display on Mac OS X.

Syntax:
@example
      set terminal aqua @{<n>@} @{title "<wintitle>"@} @{size <x> <y>@}
                        @{font "<fontname>@{,<fontsize>@}"@}
                        @{@{no@}enhanced@} @{solid|dashed@} @{dl <dashlength>@}@}

@end example

where <n> is the number of the window to draw in (default is 0),
<wintitle> is the name shown in the title bar (default "Figure <n>"),
<x> <y> is the size of the plot (default is 846x594 pt = 11.75x8.25 in).

Use <fontname> to specify the font to use (default is "Times-Roman"),
and <fontsize> to specify the font size (default is 14.0 pt). The old syntax
@{fname "<fontname>"@} @{fsize <fontsize>@} is still supported.

The aqua terminal supports enhanced text mode (see `enhanced`), except for
overprint. Font support is limited to the fonts available on the system.
Character encoding can be selected by @ref{encoding} and currently supports
iso_latin_1, iso_latin_2, cp1250, and default which equals UTF8.

Lines can be drawn either solid or dashed, (default is solid) and the dash
spacing can be modified by <dashlength> which is a multiplier > 0.


@node atari_ST_(via_AES), atari_ST_(via_VDI), aqua, terminal_
@subsubsection atari ST (via AES)

@c ?commands set terminal atari
@c ?set terminal atari
@c ?set term atari
@c ?terminal atari
@c ?term atari
@cindex atari
@tmindex atari


The `atari` terminal has options to set the character size and the screen
colors.

Syntax:
@example
      set terminal atari @{<fontsize>@} @{<col0> <col1> ... <col15>@}

@end example

The character size must appear if any colors are to be specified.  Each of
the (up to 16) colors is given as a three-digit hex number, where the digits
represent RED, GREEN and BLUE (in that order).  The range of 0--15 is scaled
to whatever color range the screen actually has.  On a normal ST screen, odd
and even intensities are the same.

Examples:
@example
      set terminal atari 4    # use small (6x6) font
      set terminal atari 6 0  # set monochrome screen to white on black
      set terminal atari 13 0 fff f00 f0 f ff f0f
                 # set first seven colors to black, white, red, green,
                 # blue, cyan, and purple and use large font (8x16).

@end example

Additionally, if an environment variable GNUCOLORS exists, its contents are
interpreted as an options string, but an explicit terminal option takes
precedence."

@node atari_ST_(via_VDI), be, atari_ST_(via_AES), terminal_
@subsubsection atari ST (via VDI)

@c ?commands set terminal vdi
@c ?set terminal vdi
@c ?set term vdi
@c ?terminal vdi
@c ?term vdi
@cindex vdi
@tmindex vdi


The `vdi` terminal is the same as the `atari` terminal, except that it sends
output to the screen via the VDI and not into AES-Windows.

The `vdi` terminal has options to set the character size and the screen
colors.

Syntax:
@example
      set terminal vdi @{<fontsize>@} @{<col0> <col1> ... <col15>@}

@end example

The character size must appear if any colors are to be specified.  Each of
the (up to 16) colors is given as a three-digit hex number, where the digits
represent RED, GREEN and BLUE (in that order).  The range of 0--15 is scaled
to whatever color range the screen actually has.  On a normal ST screen, odd
and even intensities are the same.

Examples:
@example
      set terminal vdi 4    # use small (6x6) font
      set terminal vdi 6 0  # set monochrome screen to white on black
      set terminal vdi 13 0 fff f00 f0 f ff f0f
                 # set first seven colors to black, white, red, green,
                 # blue, cyan, and purple and use large font (8x16).

@end example

Additionally, if an environment variable GNUCOLORS exists, its contents are
interpreted as an options string, but an explicit terminal option takes
precedence."

@node be, cgi, atari_ST_(via_VDI), terminal_
@subsubsection be

@c ?commands set terminal be
@c ?set terminal be
@c ?set term be
@c ?terminal be
@c ?term be
@cindex be

@cindex BE

`gnuplot` provides the `be` terminal type for use with X servers.  This
terminal type is set automatically at startup if the `DISPLAY` environment
variable is set, if the `TERM` environment variable is set to `xterm`, or
if the `-display` command line option is used.

Syntax:
@example
          set terminal be @{reset@} @{<n>@}

@end example

Multiple plot windows are supported: `set terminal be <n>` directs the
output to plot window number n.  If n>0, the terminal number will be
appended to the window title and the icon will be labeled `gplt <n>`.
The active window may distinguished by a change in cursor (from default
to crosshair.)

Plot windows remain open even when the `gnuplot` driver is changed to a
different device.  A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing `close` from a window
manager menu.  All plot windows can be closed by specifying @ref{reset}, which
actually terminates the subprocess which maintains the windows (unless
`-persist` was specified).

Plot windows will automatically be closed at the end of the session
unless the `-persist` option was given.

The size or aspect ratio of a plot may be changed by resizing the `gnuplot`
window.

Linewidths and pointsizes may be changed from within `gnuplot` with
`set linestyle`.

For terminal type `be`, `gnuplot` accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file.  See the X(1) man page
(or its equivalent) for a description of such options.

A number of other `gnuplot` options are available for the `be` terminal.
These may be specified either as command-line options when `gnuplot` is
invoked or as resources in the configuration file ".Xdefaults".  They are
set upon initialization and cannot be altered during a `gnuplot` session.


@noindent --- COMMAND-LINE_OPTIONS ---

@c ?commands set terminal be command-line-options
@c ?set terminal be command-line-options
@c ?set term be command-line-options
@c ?be command-line-options
In addition to the X Toolkit options, the following options may be specified
on the command line when starting `gnuplot` or as resources in your
".Xdefaults" file:

@example
 `-mono`        forces monochrome rendering on color displays.
 `-gray`        requests grayscale rendering on grayscale or color displays.
                        (Grayscale displays receive monochrome rendering by default.)
 `-clear`   requests that the window be cleared momentarily before a
                        new plot is displayed.
 `-raise`   raises plot window after each plot
 `-noraise` does not raise plot window after each plot
 `-persist` plots windows survive after main gnuplot program exits

@end example

The options are shown above in their command-line syntax.  When entered as
resources in ".Xdefaults", they require a different syntax.

Example:
@example
          gnuplot*gray: on

@end example

`gnuplot` also provides a command line option (`-pointsize <v>`) and a
resource, `gnuplot*pointsize: <v>`, to control the size of points plotted
with the `points` plotting style.  The value `v` is a real number (greater
than 0 and less than or equal to ten) used as a scaling factor for point
sizes.  For example, `-pointsize 2` uses points twice the default size, and
`-pointsize 0.5` uses points half the normal size.


@noindent --- MONOCHROME_OPTIONS ---

@c ?commands set terminal be monochrome_options
@c ?set terminal be monochrome_options
@c ?set term be monochrome_options
@c ?be monochrome_options
For monochrome displays, `gnuplot` does not honor foreground or background
colors.  The default is black-on-white.  `-rv` or `gnuplot*reverseVideo: on`
requests white-on-black.



@noindent --- COLOR_RESOURCES ---

@c ?commands set terminal be color_resources
@c ?set terminal be color_resources
@c ?set term be color_resources
@c ?be color_resources
For color displays, `gnuplot` honors the following resources (shown here
with their default values) or the greyscale resources.  The values may be
color names as listed in the BE rgb.txt file on your system, hexadecimal
RGB color specifications (see BE documentation), or a color name followed
by a comma and an `intensity` value from 0 to 1.  For example, `blue, 0.5`
means a half intensity blue.

@example
 gnuplot*background:  white
 gnuplot*textColor:   black
 gnuplot*borderColor: black
 gnuplot*axisColor:   black
 gnuplot*line1Color:  red
 gnuplot*line2Color:  green
 gnuplot*line3Color:  blue
 gnuplot*line4Color:  magenta
 gnuplot*line5Color:  cyan
 gnuplot*line6Color:  sienna
 gnuplot*line7Color:  orange
 gnuplot*line8Color:  coral

@end example


The command-line syntax for these is, for example,

Example:
@example
          gnuplot -background coral

@end example



@noindent --- GRAYSCALE_RESOURCES ---

@c ?commands set terminal be grayscale_resources
@c ?set terminal be grayscale_resources
@c ?set term be grayscale_resources
@c ?be grayscale_resources
When `-gray` is selected, `gnuplot` honors the following resources for
grayscale or color displays (shown here with their default values).  Note
that the default background is black.

@example
 gnuplot*background: black
 gnuplot*textGray:   white
 gnuplot*borderGray: gray50
 gnuplot*axisGray:   gray50
 gnuplot*line1Gray:  gray100
 gnuplot*line2Gray:  gray60
 gnuplot*line3Gray:  gray80
 gnuplot*line4Gray:  gray40
 gnuplot*line5Gray:  gray90
 gnuplot*line6Gray:  gray50
 gnuplot*line7Gray:  gray70
 gnuplot*line8Gray:  gray30

@end example




@noindent --- LINE_RESOURCES ---

@c ?commands set terminal be line_resources
@c ?set terminal be line_resources
@c ?set term be line_resources
@c ?be line_resources
`gnuplot` honors the following resources for setting the width (in pixels) of
plot lines (shown here with their default values.)  0 or 1 means a minimal
width line of 1 pixel width.  A value of 2 or 3 may improve the appearance of
some plots.

@example
 gnuplot*borderWidth: 2
 gnuplot*axisWidth:   0
 gnuplot*line1Width:  0
 gnuplot*line2Width:  0
 gnuplot*line3Width:  0
 gnuplot*line4Width:  0
 gnuplot*line5Width:  0
 gnuplot*line6Width:  0
 gnuplot*line7Width:  0
 gnuplot*line8Width:  0

@end example


`gnuplot` honors the following resources for setting the dash style used for
plotting lines.  0 means a solid line.  A two-digit number `jk` (`j` and `k`
are >= 1  and <= 9) means a dashed line with a repeated pattern of `j` pixels
on followed by `k` pixels off.  For example, '16' is a "dotted" line with one
pixel on followed by six pixels off.  More elaborate on/off patterns can be
specified with a four-digit value.  For example, '4441' is four on, four off,
four on, one off.  The default values shown below are for monochrome displays
or monochrome rendering on color or grayscale displays.  For color displays,
the default for each is 0 (solid line) except for `axisDashes` which defaults
to a '16' dotted line.

@example
 gnuplot*borderDashes:   0
 gnuplot*axisDashes:        16
 gnuplot*line1Dashes:        0
 gnuplot*line2Dashes:   42
 gnuplot*line3Dashes:   13
 gnuplot*line4Dashes:   44
 gnuplot*line5Dashes:   15
 gnuplot*line6Dashes: 4441
 gnuplot*line7Dashes:   42
 gnuplot*line8Dashes:   13

@end example


@node cgi, cgm, be, terminal_
@subsubsection cgi

@c ?commands set terminal cgi
@c ?set terminal cgi
@c ?set term cgi
@c ?terminal cgi
@c ?term cgi
@cindex cgi
@tmindex cgi


@c ?commands set terminal hcgi
@c ?set terminal hcgi
@c ?set term hcgi
@c ?terminal hcgi
@c ?term hcgi
@cindex hcgi
@tmindex hcgi


The `cgi` and `hcgi` terminal drivers support SCO CGI drivers.  `hcgi` is for
printers; the environment variable CGIPRNT must be set.  `cgi` may be used
for either a display or hardcopy; if the environment variable CGIDISP is set,
then that display is used.  Otherwise CGIPRNT is used.

These terminals have no options."

@node cgm, corel, cgi, terminal_
@subsubsection cgm

@c ?commands set terminal cgm
@c ?set terminal cgm
@c ?set term cgm
@c ?terminal cgm
@c ?term cgm
@cindex cgm
@tmindex cgm


The `cgm` terminal generates a Computer Graphics Metafile, Version 1. 
This file format is a subset of the ANSI X3.122-1986 standard entitled
"Computer Graphics - Metafile for the Storage and Transfer of Picture
Description Information".

Syntax:
@example
      set terminal cgm @{color | monochrome@} @{solid | dashed@} @{@{no@}rotate@}
                       @{<mode>@} @{width <plot_width>@} @{linewidth <line_width>@}
                       @{font "<fontname>,<fontsize>"@}
                       @{<color0> <color1> <color2> ...@}

@end example

`solid` draws all curves with solid lines, overriding any dashed patterns;
<mode> is `landscape`, `portrait`, or `default`;
<plot_width> is the assumed width of the plot in points; 
<line_width> is the line width in points (default 1); 
<fontname> is the name of a font (see list of fonts below)
<fontsize> is the size of the font in points (default 12).

The first six options can be in any order.  Selecting `default` sets all
options to their default values.

Each color must be of the form 'xrrggbb', where x is the literal
character 'x' and 'rrggbb' are the red, green and blue components in
hex.  For example, 'x00ff00' is green.  The background color is set
first, then the plotting colors.

Examples:
@example
      set terminal cgm landscape color rotate dashed width 432 \\
                     linewidth 1  'Helvetica Bold' 12       # defaults
      set terminal cgm linewidth 2  14  # wider lines & larger font
      set terminal cgm portrait "Times Italic" 12
      set terminal cgm color solid      # no pesky dashes!

@end example



@noindent --- CGM FONTS ---

@c ?commands set terminal cgm font
@c ?set terminal cgm font
@c ?set term cgm font
@c ?cgm font
The first part of a Computer Graphics Metafile, the metafile description,
includes a font table.  In the picture body, a font is designated by an
index into this table.  By default, this terminal generates a table with
the following 35 fonts, plus six more with `italic` replaced by
`oblique`, or vice-versa (since at least the Microsoft Office and Corel
Draw CGM import filters treat `italic` and `oblique` as equivalent):

@example
      Helvetica
      Helvetica Bold
      Helvetica Oblique
      Helvetica Bold Oblique
      Times Roman
      Times Bold
      Times Italic
      Times Bold Italic
      Courier
      Courier Bold
      Courier Oblique
      Courier Bold Oblique
      Symbol
      Hershey/Cartographic_Roman
      Hershey/Cartographic_Greek
      Hershey/Simplex_Roman
      Hershey/Simplex_Greek
      Hershey/Simplex_Script
      Hershey/Complex_Roman
      Hershey/Complex_Greek
      Hershey/Complex_Script
      Hershey/Complex_Italic
      Hershey/Complex_Cyrillic
      Hershey/Duplex_Roman
      Hershey/Triplex_Roman
      Hershey/Triplex_Italic
      Hershey/Gothic_German
      Hershey/Gothic_English
      Hershey/Gothic_Italian
      Hershey/Symbol_Set_1
      Hershey/Symbol_Set_2
      Hershey/Symbol_Math
      ZapfDingbats
      Script
      15

@end example


The first thirteen of these fonts are required for WebCGM.  The
Microsoft Office CGM import filter implements the 13 standard fonts
listed above, and also 'ZapfDingbats' and 'Script'.  However, the
script font may only be accessed under the name '15'.  For more on
Microsoft import filter font substitutions, check its help file which
you may find here:
@example
  C:\\Program Files\\Microsoft Office\\Office\\Cgmimp32.hlp
@end example

and/or its configuration file, which you may find here:
@example
  C:\\Program Files\\Common Files\\Microsoft Shared\\Grphflt\\Cgmimp32.cfg

@end example

In the `set term` command, you may specify a font name which does not
appear in the default font table.  In that case, a new font table is
constructed with the specified font as its first entry. You must ensure
that the spelling, capitalization, and spacing of the name are
appropriate for the application that will read the CGM file.  (Gnuplot
and any MIL-D-28003A compliant application ignore case in font names.)
If you need to add several new fonts, use several `set term` commands.

Example:
@example
      set terminal cgm 'Old English'
      set terminal cgm 'Tengwar'
      set terminal cgm 'Arabic'
      set output 'myfile.cgm'
      plot ...
      set output

@end example

You cannot introduce a new font in a @ref{label} command.



@noindent --- CGM FONTSIZE ---

@c ?commands set terminal cgm fontsize
@c ?set terminal cgm fontsize
@c ?set term cgm fontsize
@c ?cgm fontsize
Fonts are scaled assuming the page is 6 inches wide.  If the @ref{size}
command is used to change the aspect ratio of the page or the CGM file
is converted to a different width, the resulting font sizes will be
scaled up or down accordingly.  To change the assumed width, use the
`width` option.



@noindent --- CGM LINEWIDTH ---

@c ?commands set terminal cgm linewidth
@c ?set terminal cgm linewidth
@c ?set term cgm linewidth
@c ?cgm linewidth
The `linewidth` option sets the width of lines in pt.  The default width
is 1 pt.  Scaling is affected by the actual width of the page, as
discussed under the `fontsize` and `width` options.



@noindent --- CGM ROTATE ---

@c ?commands set terminal cgm rotate
@c ?set terminal cgm rotate
@c ?set term cgm rotate
@c ?cgm rotate
The `norotate` option may be used to disable text rotation.  For
example, the CGM input filter for Word for Windows 6.0c can accept
rotated text, but the DRAW editor within Word cannot.  If you edit a
graph (for example, to label a curve), all rotated text is restored to
horizontal.  The Y axis label will then extend beyond the clip boundary.
With `norotate`, the Y axis label starts in a less attractive location,
but the page can be edited without damage.  The `rotate` option confirms
the default behavior.



@noindent --- CGM SOLID ---

@c ?set terminal cgm solid
@c ?set term cgm solid
@c ?cgm solid
The `solid` option may be used to disable dashed line styles in the
plots.  This is useful when color is enabled and the dashing of the
lines detracts from the appearance of the plot. The `dashed` option
confirms the default behavior, which gives a different dash pattern to
each line type.



@noindent --- CGM SIZE ---

@c ?commands set terminal cgm size
@c ?set terminal cgm size
@c ?set term cgm size
@c ?cgm size
Default size of a CGM plot is 32599 units wide and 23457 units high for
landscape, or 23457 units wide by 32599 units high for portrait.



@noindent --- CGM WIDTH ---

@c ?commands set terminal cgm width
@c ?set terminal cgm width
@c ?set term cgm width
@c ?cgm width
All distances in the CGM file are in abstract units.  The application
that reads the file determines the size of the final plot.  By default,
the width of the final plot is assumed to be 6 inches (15.24 cm).  This
distance is used to calculate the correct font size, and may be changed
with the `width` option.  The keyword should be followed by the width in
points.  (Here, a point is 1/72 inch, as in PostScript.  This unit is
known as a "big point" in TeX.)  Gnuplot `expressions` can be used to
convert from other units.

Example:
@example
      set terminal cgm width 432            # default
      set terminal cgm width 6*72           # same as above
      set terminal cgm width 10/2.54*72     # 10 cm wide

@end example



@noindent --- CGM NOFONTLIST ---

@c ?commands set terminal cgm nofontlist
@c ?set terminal cgm nofontlist
@c ?set term cgm nofontlist
@c ?cgm nofontlist
@c ?set terminal cgm winword6
@c ?set term cgm winword6
@c ?cgm winword6
The default font table includes the fonts recommended for WebCGM, which
are compatible with the Computer Graphics Metafile input filter for
Microsoft Office and Corel Draw.  Another application might use
different fonts and/or different font names, which may not be
documented.  The `nofontlist` (synonym `winword6`) option deletes the font
table from the CGM file.  In this case, the reading application should
use a default table.  Gnuplot will still use its own default font table
to select font indices.  Thus, 'Helvetica' will give you an index of 1,
which should get you the first entry in your application's default font
table. 'Helvetica Bold' will give you its second entry, etc.



@node corel, debug, cgm, terminal_
@subsubsection corel

@c ?commands set terminal corel
@c ?set terminal corel
@c ?set term corel
@c ?terminal corel
@c ?term corel
@cindex corel
@tmindex corel


The `corel` terminal driver supports CorelDraw.

Syntax:
@example
      set terminal corel @{  default
                          | @{monochrome | color
                               @{"<font>" @{<fontsize> 
                                  @{<xsize> <ysize> @{<linewidth> @}@}@}@}@}

@end example

where the fontsize and linewidth are specified in points and the sizes in
inches.  The defaults are monochrome, "SwitzerlandLight", 22, 8.2, 10 and 1.2."

@node debug, svga, corel, terminal_
@subsubsection debug

@c ?commands set terminal debug
@c ?set terminal debug
@c ?set term debug
@c ?terminal debug
@c ?term debug
@cindex debug
@tmindex debug


This terminal is provided to allow for the debugging of `gnuplot`.  It is
likely to be of use only for users who are modifying the source code."

@node svga, dumb, debug, terminal_
@subsubsection svga

@c ?commands set terminal svga
@c ?set terminal svga
@c ?set term svga
@c ?terminal svga
@c ?term svga
@cindex svga
@tmindex svga


The `svga` terminal driver supports PCs with SVGA graphics.  It can only be
used if it is compiled with DJGPP.  Its only option is the font.

Syntax:
@example
      set terminal svga @{"<fontname>"@}"

@end example

@node dumb, dxf, svga, terminal_
@subsubsection dumb

@c ?commands set terminal dumb
@c ?set terminal dumb
@c ?set term dumb
@c ?terminal dumb
@c ?term dumb
@cindex dumb
@tmindex dumb


The `dumb` terminal driver has an optional size specification and trailing
linefeed control.

Syntax:
@example
      set terminal dumb @{[no]feed@} @{<xsize> <ysize>@}
                        @{[no]enhanced@}

@end example

where <xsize> and <ysize> set the size of the dumb terminals. Default is
79 by 24. The last newline is printed only if `feed` is enabled.

Examples:
@example
      set term dumb nofeed
      set term dumb 79 49 # VGA screen---why would anyone do that?"

@end example

@node dxf, dxy800a, dumb, terminal_
@subsubsection dxf

@c ?commands set terminal dxf
@c ?set terminal dxf
@c ?set term dxf
@c ?terminal dxf
@c ?term dxf
@cindex dxf
@tmindex dxf


The `dxf` terminal driver creates pictures that can be imported into AutoCad
(Release 10.x).  It has no options of its own, but some features of its plots
may be modified by other means.  The default size is 120x80 AutoCad units,
which can be changed by @ref{size}.  `dxf` uses seven colors (white, red,
yellow, green, cyan, blue and magenta), which can be changed only by
modifying the source file.  If a black-and-white plotting device is used, the
colors are mapped to differing line thicknesses.  See the description of the
AutoCad print/plot command."

@node dxy800a, eepic, dxf, terminal_
@subsubsection dxy800a

@c ?commands set terminal dxy800a
@c ?set terminal dxy800a
@c ?set term dxy800a
@c ?terminal dxy800a
@c ?term dxy800a
@cindex dxy800a
@tmindex dxy800a


This terminal driver supports the Roland DXY800A plotter.  It has no options."

@node eepic, emf, dxy800a, terminal_
@subsubsection eepic

@c ?commands set terminal eepic
@c ?set terminal eepic
@c ?set term eepic
@c ?terminal eepic
@c ?term eepic
@cindex eepic
@tmindex eepic


The `eepic` terminal driver supports the extended LaTeX picture environment.
It is an alternative to the `latex` driver.

The output of this terminal is intended for use with the "eepic.sty" macro
package for LaTeX.  To use it, you need "eepic.sty", "epic.sty" and a
printer driver that supports the "tpic" \\specials.  If your printer driver
doesn't support those \\specials, "eepicemu.sty" will enable you to use some
of them.
dvips and dvipdfm do support the "tpic" \\specials.

Syntax:
@example
   set terminal eepic @{color, dashed, rotate, small, tiny, default, <fontsize>@}

@end example

Options:
You can give options in any order you wish.
'color' causes gnuplot to produce \\color@{...@} commands so that the graphs are
colored. Using this option, you must include \\usepackage@{color@} in the preambel
of your latex document.
'dashed' will allow dashed line types; without this option, only solid lines
with varying thickness will be used.
'dashed' and 'color' are mutually exclusive; if 'color' is specified, then 'dashed'
will be ignored.
'rotate' will enable true rotated text (by 90 degrees). Otherwise, rotated text
will be typeset with letters stacked above each other. If you use this option
you must include \\usepackage@{graphicx@} in the preamble.
'small' will use \\scriptsize symbols as point markers (Probably does not work
with TeX, only LaTeX2e). Default is to use the default math size.
'tiny' uses \\scriptscriptstyle symbols.
'default' resets all options to their defaults = no color, no dashed lines,
pseudo-rotated (stacked) text, large point symbols.
<fontsize> is a number which specifies the font size inside the picture
environment; the unit is pt (points), i.e., 10 pt equals approx. 3.5 mm.
If fontsize is not specified, then all text inside the picture will be set
in \\footnotesize.

Notes:
Remember to escape the # character (or other chars meaningful to (La-)TeX)
by \\\\ (2 backslashes).
It seems that dashed lines become solid lines when the vertices of a plot
are too close. (I do not know if that is a general problem with the tpic specials,
or if it is caused by a bug in eepic.sty or dvips/dvipdfm.)
The default size of an eepic plot is 5x3 inches, which can be scaled 
by 'set size a,b'.
Points, among other things, are drawn using the LaTeX commands "\\Diamond",
"\\Box", etc.  These commands no longer belong to the LaTeX2e core; they are
included in the latexsym package, which is part of the base distribution and
thus part of any LaTeX implementation. Please do not forget to use this package.
Instead of latexsym, you can also include the amssymb package.
All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '@{', you also need to include a '@}' at the
end of the text, and the whole text will be centered both horizontally and
vertically.  If the text string begins with '[', you need to follow this with
a position specification (up to two out of t,b,l,r), ']@{', the text itself,
and finally '@}'.  The text itself may be anything LaTeX can typeset as an
LR-box.  '\\rule@{@}@{@}'s may help for best positioning.

Examples:
set term eepic
@example
  output graphs as eepic macros inside a picture environment;
  \\input the resulting file in your LaTeX document.
@end example

set term eepic color tiny rotate 8
@example
  eepic macros with \\color macros, \\scripscriptsize point markers,
  true rotated text, and all text set with 8pt.

@end example

About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
@example
       set title '\\LaTeX\\ -- $ \\gamma $'
@end example

Force centering both horizontally and vertically:
@example
       set label '@{\\LaTeX\\ -- $ \\gamma $@}' at 0,0
@end example

Specify own positioning (top here):
@example
       set xlabel '[t]@{\\LaTeX\\ -- $ \\gamma $@}'
@end example

The other label -- account for long ticlabels:
@example
       set ylabel '[r]@{\\LaTeX\\ -- $ \\gamma $\\rule@{7mm@}@{0pt@}@}'"

@end example

@node emf, emxvga, eepic, terminal_
@subsubsection emf

@c ?commands set terminal emf
@c ?set terminal emf
@c ?set term emf
@c ?terminal emf
@c ?term emf
@cindex emf
@tmindex emf


The `emf` terminal generates an Enhanced Metafile Format file.
This file format is recognized by many Windows applications.

Syntax:
@example
      set terminal emf @{color | monochrome@} @{solid | dashed@}
                       @{enhanced @{noproportional@}@}
                       @{linewidth <LW>@} @{dashlength <DL>@} @{size XX,YY@}
                       @{"<fontname>"@} @{<fontsize>@}    #old syntax
                       @{font "<fontname>,<fontsize>"@} #new syntax

@end example

In `monochrome` mode successive line types cycle through dash patterns.
In `color` mode successive line types use successive colors, and only after
all 8 default colors are exhausted is the dash pattern incremented.
`solid` draws all curves with solid lines, overriding any dashed patterns;
`linewidth <factor>` multiplies all line widths by this factor.
`dashlength <factor>` is useful for thick lines.
<font> is the name of a font; and 
`<fontsize>` is the size of the font in points.

The nominal size of the output image defaults to 1024x768 in arbitrary
units. You may specify a different nominal size using the @ref{size} option.

Enhanced text mode tries to approximate proportional character spacing.
If you are using a monospaced font, or don't like the approximation, you
can turn off this correction using the `noproportional` option.

The default settings are `color dashed font "Arial,12" size 1024,768`
Selecting `default` sets all options to their default values.

Examples:
@example
      set terminal emf 'Times Roman Italic' 12
      set terminal emf color solid    # no pesky dashes!"

@end example

@node emxvga, epson-180dpi, emf, terminal_
@subsubsection emxvga

@c ?commands set terminal emxvga
@c ?set terminal emxvga
@c ?set term emxvga
@c ?terminal emxvga
@c ?term emxvga
@cindex emxvga
@tmindex emxvga


@c ?commands set terminal emxvesa
@c ?set terminal emxvesa
@c ?set term emxvesa
@c ?terminal emxvesa
@c ?term emxvesa
@cindex emxvesa
@tmindex emxvesa


@c ?commands set terminal vgal
@c ?set terminal vgal
@c ?set term vgal
@c ?terminal vgal
@c ?term vgal
@cindex vgal
@tmindex vgal


The `emxvga`, `emxvesa` and `vgal` terminal drivers support PCs with SVGA,
vesa SVGA and VGA graphics boards, respectively.  They are intended to be
compiled with "emx-gcc" under either DOS or OS/2.  They also need VESA and
SVGAKIT maintained by Johannes Martin (JMARTIN@@GOOFY.ZDV.UNI-MAINZ.DE) with
additions by David J. Liu (liu@@phri.nyu.edu).

Syntax:
@example
      set terminal emxvga
      set terminal emxvesa @{vesa-mode@}
      set terminal vgal

@end example

The only option is the vesa mode for `emxvesa`, which defaults to G640x480x256."

@node epson-180dpi, excl, emxvga, terminal_
@subsubsection epson-180dpi

@c ?commands set terminal epson-180dpi
@c ?set terminal epson-180dpi
@c ?set term epson-180dpi
@c ?terminal epson-180dpi
@c ?term epson-180dpi
@cindex epson-180dpi
@tmindex epson-180dpi


@c ?commands set terminal epson-60dpi
@c ?set terminal epson-60dpi
@c ?set term epson-60dpi
@c ?terminal epson-60dpi
@c ?term epson-60dpi
@cindex epson-60dpi
@tmindex epson-60dpi


@c ?commands set terminal epson-lx800
@c ?set terminal epson-lx800
@c ?set term epson-lx800
@c ?terminal epson-lx800
@c ?term epson-lx800
@cindex epson-lx800
@tmindex epson-lx800


@c ?commands set terminal nec-cp6
@c ?set terminal nec-cp6
@c ?set term nec-cp6
@c ?terminal nec-cp6
@c ?term nec-cp6
@cindex nec-cp6
@tmindex nec-cp6


@c ?commands set terminal okidata
@c ?set terminal okidata
@c ?set term okidata
@c ?terminal okidata
@c ?term okidata
@cindex okidata
@tmindex okidata


@c ?commands set terminal starc
@c ?set terminal starc
@c ?set term starc
@c ?terminal starc
@c ?term starc
@cindex starc
@tmindex starc


@c ?commands set terminal tandy-60dpi
@c ?set terminal tandy-60dpi
@c ?set term tandy-60dpi
@c ?terminal tandy-60dpi
@c ?term tandy-60dpi
@cindex tandy-60dpi
@tmindex tandy-60dpi


This driver supports a family of Epson printers and derivatives.

`epson-180dpi` and `epson-60dpi` are drivers for Epson LQ-style 24-pin
printers with resolutions of 180 and 60 dots per inch, respectively.

`epson-lx800` is a generic 9-pin driver appropriate for printers like the
Epson LX-800, the Star NL-10 and NX-1000, the PROPRINTER, and so forth.

`nec-cp6` is generic 24-pin driver that can be used for printers like the
NEC CP6 and the Epson LQ-800.

The `okidata` driver supports the 9-pin OKIDATA 320/321 Standard printers.

The `starc` driver is for the Star Color Printer.

The `tandy-60dpi` driver is for the Tandy DMP-130 series of 9-pin, 60-dpi
printers.

Only `nec-cp6` has any options.

Syntax:
@example
      set terminal nec-cp6 @{monochrome | colour | draft@}

@end example

which defaults to monochrome.

With each of these drivers, a binary copy is required on a PC to print.  Do
not use @ref{print}---use instead `copy file /b lpt1:`."

@node excl, hercules, epson-180dpi, terminal_
@subsubsection excl

@c ?commands set terminal excl
@c ?set terminal excl
@c ?set term excl
@c ?terminal excl
@c ?term excl
@cindex excl
@tmindex excl


The `excl` terminal driver supports Talaris printers such as the EXCL Laser
printer and the 1590.  It has no options."

@node hercules, fig, excl, terminal_
@subsubsection hercules

@c ?commands set terminal hercules
@c ?set terminal hercules
@c ?set term hercules
@c ?terminal hercules
@c ?term hercules
@cindex hercules
@tmindex hercules


@c ?commands set terminal egalib
@c ?set terminal egalib
@c ?set term egalib
@c ?terminal egalib
@c ?term egalib
@cindex egalib
@tmindex egalib


@c ?commands set terminal egamono
@c ?set terminal egamono
@c ?set term egamono
@c ?terminal egamono
@c ?term egamono
@cindex egamono
@tmindex egamono


@c ?commands set terminal vgalib
@c ?set terminal vgalib
@c ?set term vgalib
@c ?terminal vgalib
@c ?term vgalib
@cindex vgalib
@tmindex vgalib


@c ?commands set terminal vgamono
@c ?set terminal vgamono
@c ?set term vgamono
@c ?terminal vgamono
@c ?term vgamono
@cindex vgamono
@tmindex vgamono


@c ?commands set terminal svgalib
@c ?set terminal svgalib
@c ?set term svgalib
@c ?terminal svgalib
@c ?term svgalib
@cindex svgalib
@tmindex svgalib


@c ?commands set terminal ssvgalib
@c ?set terminal ssvgalib
@c ?set term ssvgalib
@c ?terminal ssvgalib
@c ?term ssvgalib
@cindex ssvgalib
@tmindex ssvgalib


These drivers supports PC monitors with autodetected graphics boards.  They
can be used only when compiled with Zortech C/C++.  None have options."

@node fig, png, hercules, terminal_
@subsubsection fig

@c ?commands set terminal fig
@c ?set terminal fig
@c ?set term fig
@c ?terminal fig
@c ?term fig
@cindex fig

@cindex xfig

The `fig` terminal device generates output in the Fig graphics language.

Syntax:
@example
      set terminal fig @{monochrome | color@}
                       @{landscape | portrait@}
                       @{small | big | size <xsize> <ysize>@}
                       @{metric | inches@}
                       @{pointsmax <max_points>@}
                       @{solid | dashed@}
                       @{font <fontname>@} @{fontsize <fsize>@}
                       @{textnormal | @{textspecial texthidden textrigid@}@}
                       @{@{thickness|linewidth@} <units>@}
                       @{depth <layer>@}
                       @{version <number>@}

@end example

`monochrome` and `color` determine whether the picture is black-and-white or
`color`.  `small` and `big` produce a 5x3 or 8x5 inch graph in the default
`landscape` mode and 3x5 or 5x8 inches in `portrait` mode.
@ref{size} sets (overrides) the size of the drawing
area to <xsize>*<ysize> in units of inches or centimeters depending on the
`inches` or `metric` setting in effect.
The latter settings is also used as default units for editing with "xfig".

`pointsmax <max_points>` sets the maximum number of points per polyline.

`solid` inhibits automatic usage of `dash`ed lines when solid linestyles are
used up, which otherwise occurs.

`fontsize` sets the size of the text font to <fsize> points.  `textnormal`
resets the text flags and selects postscript fonts, `textspecial` sets the
text flags for LaTeX specials, `texthidden` sets the hidden flag and
`textrigid` the rigid flag. 

`depth` sets the default depth layer for all lines and text.  The default
depth is 10 to leave room for adding material with "xfig" on top of the
plot.

@ref{version} sets the format version of the generated fig output. Currently
only versions 3.1 and 3.2 are supported.

`thickness` sets the default line thickness, which is 1 if not specified.
Overriding the thickness can be achieved by adding a multiple of 100 to the
`linetype` value for a `plot` command.  In a similar way the `depth`
of plot elements (with respect to the default depth) can be controlled by
adding a multiple of 1000 to <linetype>.  The depth is then <layer> +
<linetype>/1000 and the thickness is (<linetype>%1000)/100 or, if that is
zero, the default line thickness. `linewidth` is a synonym for `thickness`.

Additional point-plot symbols are also available with the `fig` driver. The
symbols can be used through `pointtype` values % 100 above 50, with different
fill intensities controlled by <pointtype> % 5 and outlines in black (for
<pointtype> % 10 < 5) or in the current color.  Available symbols are
@example
        50 - 59:  circles
        60 - 69:  squares
        70 - 79:  diamonds
        80 - 89:  upwards triangles
        90 - 99:  downwards triangles
@end example

The size of these symbols is linked to the font size.  The depth of symbols
is by default one less than the depth for lines to achieve nice error bars.
If <pointtype> is above 1000, the depth is <layer> + <pointtype>/1000-1.  If
<pointtype>%1000 is above 100, the fill color is (<pointtype>%1000)/100-1.

Available fill colors are (from 1 to 9): black, blue, green, cyan, red,
magenta, yellow, white and dark blue (in monochrome mode: black for 1 to 6
and white for 7 to 9).

See @ref{with} for details of <linetype> and <pointtype>.

The `big` option is a substitute for the `bfig` terminal in earlier versions,
which is no longer supported.

Examples:
@example
      set terminal fig monochrome small pointsmax 1000  # defaults

@end example

@example
      plot 'file.dat' with points linetype 102 pointtype 759
@end example

would produce circles with a blue outline of width 1 and yellow fill color.

@example
      plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 554
@end example

would produce errorbars with black lines and circles filled red.  These
circles are one layer above the lines (at depth 9 by default).

To plot the error bars on top of the circles use
@example
      plot 'file.dat' using 1:2:3 with err linetype 1 pointtype 2554"

@end example

@node png, ggi, fig, terminal_
@subsubsection png

@c ?commands set terminal png
@c ?set terminal png
@c ?set term png
@c ?terminal png
@c ?term png
@cindex png
@tmindex png


Syntax:
@example
      set terminal png 
             @{@{no@}transparent@} @{@{no@}interlace@}
             @{@{no@}truecolor@} @{rounded|butt@}
             @{tiny | small | medium | large | giant@}
             @{font <face> @{<pointsize>@}@}
             @{size <x>,<y>@} @{@{no@}crop@}
             @{@{no@}enhanced@}
             @{<color0> <color1> <color2> ...@}

@end example

PNG images are created using libgd, with optional support for TrueType
and Adobe Type 1 fonts via libfreetype. Version 1.8 or greater of libgd
is required.

`transparent` instructs the driver to generate transparent PNGs.  The first
color will be the transparent one. Default is `notransparent`.

`interlace` instructs the driver to generate interlaced PNGs.
Default is `nointerlace`.

`butt` instructs the driver to use a line drawing method that does
not overshoot the desired end point of a line.  This setting is only
applicable for line widths greater than 1.  This setting is most useful when
drawing horizontal or vertical lines.  Default is `rounded`.
Version 2.0 or greater of libgd is required.

PNG plots may be conveniently viewed by piping the output to the
'display' program from the ImageMagick package as follows:
@example
               set term png
               set output '| display png:-'

@end example

View the output from successive plot commands interactively by hitting
<space> in the display window.  To save a particular one to disk, left
click in the display window and choose @ref{save}.

Five basic fonts are supported directly by the gd library. These are
`tiny` (5x8 pixels), `small` (6x12 pixels), `medium`, (7x13 Bold), 
`large` (8x16) or `giant` (9x15 pixels). These fonts cannot be scaled
or rotated (pure horizontal or vertical text only).

@cindex fonts

If gnuplot was built with support for TrueType (*.ttf) or Adobe Type 1 
(*.pfa) fonts, they may be selected using the 'font <face> @{<pointsize>@}' 
option. <face> is either the full pathname to the font file, or a font 
face name that is assumed to be the first part of a filename in one of the 
directories listed in the GDFONTPATH environmental variable. That is, 
'set term png font "Face"' will look for a font file named either 
<somedirectory>/Face.ttf or <somedirectory>/Face.pfa. Both TrueType and 
Adobe Type 1 fonts are fully scalable and may be rotated through any angle.
If no font is specified, gnuplot checks the environmental variable 
GNUPLOT_DEFAULT_GDFONT to see if there is a preferred default font. 

`enhanced` enables the enhanced text processing features, (subscripts, 
superscripts and mixed fonts). See `enhanced` for more information. 
The full enhanced mode syntax is supported by the PNG/JPEG driver itself,
but some of these features are dependent on which version of the 
underlying libgd library is present, and which fonts are available.

The size <x,y> is given in pixels---it defaults to 640x480.  The number of
pixels can be also modified by scaling with the @ref{size} command.
`crop` trims blank space from the edges of the completed plot, resulting
in a smaller final image size. Default is `nocrop`.

Each color must be of the form 'xrrggbb', where x is the literal character
'x' and 'rrggbb' are the red, green and blue components in hex.  For example,
'x00ff00' is green.  The background color is set first, then the border
colors, then the X & Y axis colors, then the plotting colors.  The maximum
number of colors that can be set is 256.

Examples:
@example
      set terminal png medium size 640,480 \\
                       xffffff x000000 x404040 \\
                       xff0000 xffa500 x66cdaa xcdb5cd \\
                       xadd8e6 x0000ff xdda0dd x9500d3    # defaults

@end example

which uses white for the non-transparent background, black for borders, gray
for the axes, and red, orange, medium aquamarine, thistle 3, light blue, blue,
plum and dark violet for eight plotting colors.

@example
      set terminal png font arial 14 size 800,600

@end example

which searches for a TrueType font with face name 'arial' in the directory
specified by the environment variable GDFONTPATH and 14pt font size.

@example
      set terminal png transparent xffffff \\
                       x000000 x202020 x404040 x606060 \\
                       x808080 xA0A0A0 xC0C0C0 xE0E0E0

@end example

which uses white for the transparent background, black for borders, dark
gray for axes, and a gray-scale for the six plotting colors.


@node ggi, Gnugraph(GNU_plotutils), png, terminal_
@subsubsection ggi

@c ?commands set terminal ggi
@c ?set terminal ggi
@c ?set term ggi
@c ?terminal ggi
@c ?term ggi
@cindex ggi
@tmindex ggi


The `ggi` driver can run on different targets as X or svgalib.

Syntax:
@example
   set terminal ggi [acceleration <integer>] [[mode] @{mode@}]

@end example

In X the window cannot be resized using window manager handles, but the
mode can be given with the mode option, e.g.:
@example
 - V1024x768
 - V800x600
 - V640x480
 - V320x200
@end example

Please refer to the ggi documentation for other modes. The 'mode' keyword
is optional. It is recommended to select the target by environment variables
as explained in the libggi manual page. To get DGA on X, you should for
example
@example
   bash> export GGI_DISPLAY=DGA
   csh>  setenv GGI_DISPLAY DGA

@end example

'acceleration' is only used for targets which report relative pointer
motion events (e.g. DGA) and is a strictly positive integer multiplication
factor for the relative distances.  The default for acceleration is 7.

Examples:
@example
   set term ggi acc 10
   set term ggi acc 1 mode V1024x768
   set term ggi V1024x768"

@end example

@node Gnugraph(GNU_plotutils), gpic, ggi, terminal_
@subsubsection Gnugraph(GNU plotutils)

@c ?commands set terminal gnugraph
@c ?set terminal gnugraph
@c ?set term gnugraph
@c ?terminal gnugraph
@c ?term gnugraph
@cindex gnugraph
@tmindex gnugraph


The `gnugraph` driver produces device-independent output in the GNU plot
graphics language.  The default size of the PostScript results generated by
"plot2ps" is 5 x 3 inches; this can be increased up to about 8.25 x 8.25 by
@ref{size}.

Syntax:
@example
      set terminal gnugraph @{"<fontname>"@} @{<fontsize>@}
                            @{type <pt>@} @{size "<size>"@}

@end example

which defaults to 10-point "Courier".

For `type`, the following options are accepted: `X`, `pnm`, `gif`, `ai`,
`ps`, `cgm`, `fig`, `pcl5`, `hpgl`, `tek`, and `meta` (default). The
@ref{size} option (default is a4) is passed straight through to plotutils, it's
the user's responsibility to provide correct values. Details can be found
in the plotutils documentation.

Examples:
@example
      set terminal gnugraph type hpgl size "a4"
      set terminal gnugraph size "a4,xoffset=-5mm,yoffset=2.0cm" type pnm

@end example

There is a non-GNU version of the `gnugraph` driver which cannot be compiled
unless this version is left out."

@node gpic, gpic_, Gnugraph(GNU_plotutils), terminal_
@subsubsection gpic

@c ?commands set terminal gpic
@c ?set terminal gpic
@c ?set term gpic
@c ?terminal gpic
@c ?term gpic
@cindex gpic
@tmindex gpic


The `gpic` terminal driver generates GPIC graphs in the Free Software
Foundations's "groff" package.  The default size is 5 x 3 inches.  The only
option is the origin, which defaults to (0,0).

Syntax:
@example
      set terminal gpic @{<x> <y>@}

@end example

where `x` and `y` are in inches.

A simple graph can be formatted using

@example
      groff -p -mpic -Tps file.pic > file.ps.

@end example

The output from pic can be pipe-lined into eqn, so it is possible to put
complex functions in a graph with the @ref{label} and `set @{x/y@}label`
commands.  For instance,

@example
      set ylab '@@space 0 int from 0 to x alpha ( t ) roman d t@@'

@end example

will label the y axis with a nice integral if formatted with the command:

@example
      gpic filename.pic | geqn -d@@@@ -Tps | groff -m[macro-package] -Tps
          > filename.ps

@end example

Figures made this way can be scaled to fit into a document.  The pic language
is easy to understand, so the graphs can be edited by hand if need be.  All
co-ordinates in the pic-file produced by `gnuplot` are given as x+gnuplotx
and y+gnuploty.  By default x and y are given the value 0.  If this line is
removed with an editor in a number of files, one can put several graphs in
one figure like this (default size is 5.0x3.0 inches):

@example
      .PS 8.0
      x=0;y=3
      copy "figa.pic"
      x=5;y=3
      copy "figb.pic"
      x=0;y=0
      copy "figc.pic"
      x=5;y=0
      copy "figd.pic"
      .PE

@end example

This will produce an 8-inch-wide figure with four graphs in two rows on top
of each other.

One can also achieve the same thing by the command

@example
      set terminal gpic x y

@end example

for example, using

@example
      .PS 6.0
      copy "trig.pic"
      .PE"

@end example

@node gpic_, gpr, gpic, terminal_
@subsubsection gpic

@c ?commands set terminal gpic
@c ?set terminal gpic
@c ?set term gpic
@c ?terminal gpic
@c ?term gpic
@cindex gpic
@tmindex gpic


The `gpic` terminal driver generates GPIC graphs in the Free Software
Foundations's "groff" package.  The default size is 5 x 3 inches.  The only
option is the origin, which defaults to (0,0).

Syntax:
@example
      set terminal gpic @{<x> <y>@}

@end example

where `x` and `y` are in inches.

A simple graph can be formatted using

@example
      groff -p -mpic -Tps file.pic > file.ps.

@end example

The output from pic can be pipe-lined into eqn, so it is possible to put
complex functions in a graph with the @ref{label} and `set @{x/y@}label`
commands.  For instance,

@example
      set ylab '@@space 0 int from 0 to x alpha ( t ) roman d t@@'

@end example

will label the y axis with a nice integral if formatted with the command:

@example
      gpic filename.pic | geqn -d@@@@ -Tps | groff -m[macro-package] -Tps
          > filename.ps

@end example

Figures made this way can be scaled to fit into a document.  The pic language
is easy to understand, so the graphs can be edited by hand if need be.  All
co-ordinates in the pic-file produced by `gnuplot` are given as x+gnuplotx
and y+gnuploty.  By default x and y are given the value 0.  If this line is
removed with an editor in a number of files, one can put several graphs in
one figure like this (default size is 5.0x3.0 inches):

@example
      .PS 8.0
      x=0;y=3
      copy "figa.pic"
      x=5;y=3
      copy "figb.pic"
      x=0;y=0
      copy "figc.pic"
      x=5;y=0
      copy "figd.pic"
      .PE

@end example

This will produce an 8-inch-wide figure with four graphs in two rows on top
of each other.

One can also achieve the same thing by the command

@example
      set terminal gpic x y

@end example

for example, using

@example
      .PS 6.0
      copy "trig.pic"
      .PE"

@end example

@node gpr, grass, gpic_, terminal_
@subsubsection gpr

@c ?commands set terminal gpr
@c ?set terminal gpr
@c ?set term gpr
@c ?terminal gpr
@c ?term gpr
@cindex gpr
@tmindex gpr


The `gpr` terminal driver supports the Apollo Graphics Primitive Resource
for a fixed-size window.  It has no options.

If a variable window size is desired, use the `apollo` terminal instead."

@node grass, hp2623a, gpr, terminal_
@subsubsection grass

@c ?commands set terminal grass
@c ?set terminal grass
@c ?set term grass
@c ?terminal grass
@c ?term grass
@cindex grass
@tmindex grass


The `grass` terminal driver gives `gnuplot` capabilities to users of the 
GRASS geographic information system.  Contact grassp-list@@moon.cecer.army.mil
for more information.  Pages are written to the current frame of the GRASS
Graphics Window.  There are no options."

@node hp2623a, hp2648, grass, terminal_
@subsubsection hp2623a

@c ?commands set terminal hp2623a
@c ?set terminal hp2623a
@c ?set term hp2623a
@c ?terminal hp2623a
@c ?term hp2623a
@cindex hp2623a
@tmindex hp2623a


The `hp2623a` terminal driver supports the Hewlett Packard HP2623A.  It has
no options."

@node hp2648, hp500c, hp2623a, terminal_
@subsubsection hp2648

@c ?commands set terminal hp2648
@c ?set terminal hp2648
@c ?set term hp2648
@c ?terminal hp2648
@c ?term hp2648
@cindex hp2648
@tmindex hp2648


The `hp2648` terminal driver supports the Hewlett Packard HP2647 and HP2648.
It has no options."

@node hp500c, hpgl, hp2648, terminal_
@subsubsection hp500c

@c ?commands set terminal hp500c
@c ?set terminal hp500c
@c ?set term hp500c
@c ?terminal hp500c
@c ?term hp500c
@cindex hp500c
@tmindex hp500c


The `hp500c` terminal driver supports the Hewlett Packard HP DeskJet 500c.
It has options for resolution and compression.

Syntax:
@example
      set terminal hp500c @{<res>@} @{<comp>@}

@end example

where `res` can be 75, 100, 150 or 300 dots per inch and `comp` can be "rle",
or "tiff".  Any other inputs are replaced by the defaults, which are 75 dpi
and no compression.  Rasterization at the higher resolutions may require a
large amount of memory."

@node hpgl, hpljii, hp500c, terminal_
@subsubsection hpgl

@c ?commands set terminal hpgl
@c ?set terminal hpgl
@c ?set term hpgl
@c ?terminal hpgl
@c ?term hpgl
@cindex hpgl
@tmindex hpgl


@c ?commands set terminal pcl5
@c ?set terminal pcl5
@c ?set term pcl5
@c ?terminal pcl5
@c ?term pcl5
@cindex pcl5
@tmindex pcl5


The `hpgl` driver produces HPGL output for devices like the HP7475A plotter.
There are two options which can be set: the number of pens and `eject`,
which tells the plotter to eject a page when done.  The default is to use 6
pens and not to eject the page when done.

The international character sets ISO-8859-1 and CP850 are recognized via
`set encoding iso_8859_1` or `set encoding cp850` (see @ref{encoding} for
details).

Syntax:
@example
      set terminal hpgl @{<number_of_pens>@} @{eject@}

@end example

The selection

@example
      set terminal hpgl 8 eject

@end example

is equivalent to the previous `hp7550` terminal, and the selection

@example
      set terminal hpgl 4

@end example

is equivalent to the previous `hp7580b` terminal.

The `pcl5` driver supports plotters such as the Hewlett-Packard Designjet
750C, the Hewlett-Packard Laserjet III, and the Hewlett-Packard Laserjet IV.
It actually uses HPGL-2, but there is a name conflict among the terminal
devices.  It has several options which must be specified in the order
indicated below:

Syntax:
@example
      set terminal pcl5 @{mode <mode>@} @{<plotsize>@}
          @{@{color @{<number_of_pens>@}@} | monochrome@} @{solid | dashed@}
          @{font <font>@} @{size <fontsize>@} @{pspoints | nopspoints@}

@end example

<mode> is `landscape` or `portrait`. <plotsize> is the physical
plotting size of the plot, which is one of the following: `letter` for
standard (8 1/2" X 11") displays, `legal` for (8 1/2" X 14") displays,
`noextended` for (36" X 48") displays (a letter size ratio) or,
`extended` for (36" X 55") displays (almost a legal size ratio).
`color` is for multi-pen (i.e. color) plots, and <number_of_pens> is
the number of pens (i.e. colors) used in color plots. `monochrome` is for
one (e.g. black) pen plots. `solid` draws all lines as solid lines, or
`dashed` will draw lines with different dashed and dotted line patterns.
<font> is `stick`, `univers`, `cg_times`, `zapf_dingbats`, `antique_olive`,
`arial`, `courier`, `garamond_antigua`, `letter_gothic`, `cg_omega`,
`albertus`, `times_new_roman`, `clarendon`, `coronet`, `marigold`,
`truetype_symbols`, or `wingdings`. <fontsize> is the font size in points.
The point type selection can be the standard default set by specifying
`nopspoints`, or the same set of point types found in the postscript terminal
by specifying `pspoints`.

Note that built-in support of some of these options is printer device
dependent. For instance, all the fonts are supposedly supported by the HP
Laserjet IV, but only a few (e.g. univers, stick) may be supported by the HP
Laserjet III and the Designjet 750C. Also, color obviously won't work on the
the laserjets since they are monochrome devices.

Defaults: landscape, noextended, color (6 pens), solid, univers, 12 point,
@example
          and nopspoints.

@end example

With `pcl5` international characters are handled by the printer; you just put
the appropriate 8-bit character codes into the text strings.  You don't need
to bother with @ref{encoding}.

HPGL graphics can be imported by many software packages."

@node hpljii, hppj, hpgl, terminal_
@subsubsection hpljii

@c ?commands set terminal hpljii
@c ?set terminal hpljii
@c ?set term hpljii
@c ?terminal hpljii
@c ?term hpljii
@cindex hpljii
@tmindex hpljii


@c ?commands set terminal hpdj
@c ?set terminal hpdj
@c ?set term hpdj
@c ?terminal hpdj
@c ?term hpdj
@cindex hpdj
@tmindex hpdj


The `hpljii` terminal driver supports the HP Laserjet Series II printer.  The
`hpdj` driver supports the HP DeskJet 500 printer.  These drivers allow a
choice of resolutions.

Syntax:
@example
      set terminal hpljii | hpdj @{<res>@}

@end example

where `res` may be 75, 100, 150 or 300 dots per inch; the default is 75.
Rasterization at the higher resolutions may require a large amount of memory.

The `hp500c` terminal is similar to `hpdj`; `hp500c` additionally supports
color and compression."

@node hppj, imagen, hpljii, terminal_
@subsubsection hppj

@c ?commands set terminal hppj
@c ?set terminal hppj
@c ?set term hppj
@c ?terminal hppj
@c ?term hppj
@cindex hppj
@tmindex hppj


The `hppj` terminal driver supports the HP PaintJet and HP3630 printers.  The
only option is the choice of font.

Syntax:
@example
      set terminal hppj @{FNT5X9 | FNT9X17 | FNT13X25@}

@end example

with the middle-sized font (FNT9X17) being the default."

@node imagen, iris4d, hppj, terminal_
@subsubsection imagen

@c ?commands set terminal imagen
@c ?set terminal imagen
@c ?set term imagen
@c ?terminal imagen
@c ?term imagen
@cindex imagen
@tmindex imagen


The `imagen` terminal driver supports Imagen laser printers.  It is capable
of placing multiple graphs on a single page.

Syntax:
@example
      set terminal imagen @{<fontsize>@} @{portrait | landscape@}
                          @{[<horiz>,<vert>]@}

@end example

where `fontsize` defaults to 12 points and the layout defaults to `landscape`.
`<horiz>` and `<vert>` are the number of graphs in the horizontal and
vertical directions; these default to unity.

Example:
@example
      set terminal imagen portrait [2,3]

@end example

puts six graphs on the page in three rows of two in portrait orientation."

@node iris4d, kyo, imagen, terminal_
@subsubsection iris4d

@c ?commands set terminal iris4d
@c ?set terminal iris4d
@c ?set term iris4d
@c ?terminal iris4d
@c ?term iris4d
@cindex iris4d
@tmindex iris4d


The `iris4d` terminal driver supports Silicon Graphics IRIS 4D computers.
Its only option is 8- or 24-bit color depth.  The default is 8.

Syntax:
@example
      set terminal iris4d @{8 | 24@}

@end example

The color depth is not really a choice -- the value appropriate for the
hardware should be selected.

When using 24-bit mode, the colors can be directly specified via the file
.gnuplot_iris4d that is searched in the current directory and then in the
home directory specified by the HOME environment variable.  This file holds
RGB values for the background, border, labels and nine plotting colors, in
that order.  For example, here is a file containing the default colors:

@example
      85   85   85     Background   (dark gray)
      0    0    0      Boundary     (black)
      170  0    170    Labeling     (magenta)
      85   255  255    Plot Color 1 (light cyan)
      170  0    0      Plot Color 2 (red)
      0    170  0      Plot Color 3 (green)
      255  85   255    Plot Color 4 (light magenta)
      255  255  85     Plot Color 5 (yellow)
      255  85   85     Plot Color 6 (light red)
      85   255  85     Plot Color 7 (light green)
      0    170  170    Plot Color 8 (cyan)
      170  170  0      Plot Color 9 (brown)

@end example

This file must have exactly 12 lines of RGB triples.  No empty lines are
allowed, and anything after the third number on a line is ignored."

@node kyo, latex, iris4d, terminal_
@subsubsection kyo

@c ?commands set terminal kyo
@c ?set terminal kyo
@c ?set term kyo
@c ?terminal kyo
@c ?term kyo
@cindex kyo
@tmindex kyo


@c ?commands set terminal prescribe
@c ?set terminal prescribe
@c ?set term prescribe
@c ?terminal prescribe
@c ?term prescribe
@cindex prescribe
@tmindex prescribe


The `kyo` and `prescribe` terminal drivers support the Kyocera laser printer.
The only difference between the two is that `kyo` uses "Helvetica" whereas
`prescribe` uses "Courier".  There are no options."

@node latex, linux, kyo, terminal_
@subsubsection latex

@c ?commands set terminal emtex
@c ?set terminal emtex
@c ?set term emtex
@c ?terminal emtex
@c ?term emtex
@cindex emtex
@tmindex emtex


@c ?commands set terminal latex
@c ?set terminal latex
@c ?set term latex
@c ?terminal latex
@c ?term latex
@cindex latex
@tmindex latex


Syntax:
@example
      set terminal @{latex | emtex@} @{default | @{courier|roman@} @{<fontsize>@}@}
                   @{size <XX>@{unit@}, <YY>@{unit@}@}

@end example

By default the plot will inherit font settings from the embedding document.
You have the option of forcing either Courier (cmtt) or Roman (cmr) fonts
instead. In this case you may also specify a fontsize.
Unless your driver is capable of building fonts at any size (e.g. dvips),
stick to the standard 10, 11 and 12 point sizes.

METAFONT users beware: METAFONT does not like odd sizes.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '@{', you also need to include a '@}' at the
end of the text, and the whole text will be centered both horizontally and
vertically.  If the text string begins with '[', you need to follow this with
a position specification (up to two out of t,b,l,r), ']@{', the text itself,
and finally '@}'.  The text itself may be anything LaTeX can typeset as an
LR-box.  '\\rule@{@}@{@}'s may help for best positioning.

Points, among other things, are drawn using the LaTeX commands "\\Diamond" and
"\\Box".  These commands no longer belong to the LaTeX2e core; they are included
in the latexsym package, which is part of the base distribution and thus part
of any LaTeX implementation.  Please do not forget to use this package.

The default size for the plot is 5 inches by 3 inches. The @ref{size} option
changes this to whatever the user requests. By default the X and Y sizes
are taken to be in inches, but other units are possible (currently only cm).

Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
@example
       set title '\\LaTeX\\ -- $ \\gamma $'
@end example

Force centering both horizontally and vertically:
@example
       set label '@{\\LaTeX\\ -- $ \\gamma $@}' at 0,0
@end example

Specify own positioning (top here):
@example
       set xlabel '[t]@{\\LaTeX\\ -- $ \\gamma $@}'
@end example

The other label -- account for long ticlabels:
@example
       set ylabel '[r]@{\\LaTeX\\ -- $ \\gamma $\\rule@{7mm@}@{0pt@}@}'"

@end example

@node linux, linux_, latex, terminal_
@subsubsection linux

@c ?commands set terminal linux
@c ?set terminal linux
@c ?set term linux
@c ?terminal linux
@c ?term linux
@cindex linux
@tmindex linux


The `linux` driver has no additional options to specify.  It looks at the
environment variable GSVGAMODE for the default mode; if not set, it uses
1024x768x256 as default mode or, if that is not possible, 640x480x16
(standard VGA)."

@node linux_, macintosh, linux, terminal_
@subsubsection linux

@c ?commands set terminal linux
@c ?set terminal linux
@c ?set term linux
@c ?terminal linux
@c ?term linux
@cindex linux
@tmindex linux


The `linux` driver has no additional options to specify.  It looks at the
environment variable GSVGAMODE for the default mode; if not set, it uses
1024x768x256 as default mode or, if that is not possible, 640x480x16
(standard VGA)."

@node macintosh, mf, linux_, terminal_
@subsubsection macintosh

@c ?set terminal macintosh
@c ?set term macintosh
@c ?terminal macintosh
@c ?term macintosh
@cindex macintosh
@tmindex macintosh


Several options may be set in the 'macintosh' driver.

Syntax:
@example
     set terminal macintosh @{singlewin | multiwin@} @{vertical | novertical@}
                            @{size <width>, <height> | default@}

@end example

'singlewin' limits the output to a single window and is useful for animations.
'multiwin' allows multiple windows.
'vertical' is only valid under the gx option. With this option, rotated text
@example
    be drawn vertically. novertical turns this option off.
 size <width>, <height> overrides the graph size set in the preferences
    dialog until it is cleared with either 'set term mac size default'
    or 'set term mac default'.

@end example

@example
 'set term mac size default' sets the window size settings to those set in
    the preferences dialog.

@end example

@example
 'set term mac default' sets all options to their default values.
    Default values: nogx, multiwin, novertical.

@end example

@example
 If you generate graphs under the multiwin option and then switch to singlewin,
 the next plot command will cause one more window to be created. This new
 window will be reused as long as singlewin is in effect. If you switch back
 to multiwin, generate some graphs, and then switch to singlewin again, the
 orginal 'singlewin' window will be resused if it is still open. Otherwise
 a new 'singlewin' window will be created. The 'singlewin' window is not numbered."

@end example

@node mf, mp, macintosh, terminal_
@subsubsection mf

@c ?commands set terminal mf
@c ?set terminal mf
@c ?set term mf
@c ?terminal mf
@c ?term mf
@cindex mf

@cindex metafont

The `mf` terminal driver creates an input file to the METAFONT program.  Thus a
figure may be used in the TeX document in the same way as is a character.

To use a picture in a document, the METAFONT program must be run with the
output file from `gnuplot` as input.  Thus, the user needs a basic knowledge
of the font creating process and the procedure for including a new font in a
document.  However, if the METAFONT program is set up properly at the local
site, an unexperienced user could perform the operation without much trouble.

The text support is based on a METAFONT character set.  Currently the
Computer Modern Roman font set is input, but the user is in principal free to
choose whatever fonts he or she needs.  The METAFONT source files for the
chosen font must be available.  Each character is stored in a separate
picture variable in METAFONT.  These variables may be manipulated (rotated,
scaled etc.) when characters are needed.  The drawback is the interpretation
time in the METAFONT program.  On some machines (i.e. PC) the limited amount
of memory available may also cause problems if too many pictures are stored.

The `mf` terminal has no options.


@noindent --- METAFONT INSTRUCTIONS ---

@c ?commands set terminal mf detailed
@c ?set terminal mf detailed
@c ?set term mf detailed
@c ?mf detailed
@c ?metafont detailed

- Set your terminal to METAFONT:
@example
  set terminal mf
@end example

- Select an output-file, e.g.:
@example
  set output "myfigures.mf"
@end example

- Create your pictures. Each picture will generate a separate character. Its
default size will be 5*3 inches. You can change the size by saying `set size
0.5,0.5` or whatever fraction of the default size you want to have.

- Quit `gnuplot`.

- Generate a TFM and GF file by running METAFONT on the output of `gnuplot`.
Since the picture is quite large (5*3 in), you will have to use a version of
METAFONT that has a value of at least 150000 for memmax.  On Unix systems
these are conventionally installed under the name bigmf.  For the following
assume that the command virmf stands for a big version of METAFONT.  For
example:

- Invoke METAFONT:
@example
    virmf '&plain'
@end example

- Select the output device: At the METAFONT prompt ('*') type:
@example
    \\mode:=CanonCX;     % or whatever printer you use
@end example

- Optionally select a magnification:
@example
    mag:=1;             % or whatever you wish
@end example

- Input the `gnuplot`-file:
@example
    input myfigures.mf
@end example

On a typical Unix machine there will usually be a script called "mf" that
executes virmf '&plain', so you probably can substitute mf for virmf &plain.
This will generate two files: mfput.tfm and mfput.$$$gf (where $$$ indicates
the resolution of your device).  The above can be conveniently achieved by
typing everything on the command line, e.g.:
virmf '&plain' '\\mode:=CanonCX; mag:=1; input myfigures.mf'
In this case the output files will be named myfigures.tfm and
myfigures.300gf.

- Generate a PK file from the GF file using gftopk:
@example
  gftopk myfigures.300gf myfigures.300pk
@end example

The name of the output file for gftopk depends on the DVI driver you use.
Ask your local TeX administrator about the naming conventions.  Next, either
install the TFM and PK files in the appropriate directories, or set your
environment variables properly.  Usually this involves setting TEXFONTS to
include the current directory and doing the same thing for the environment
variable that your DVI driver uses (no standard name here...).  This step is
necessary so that TeX will find the font metric file and your DVI driver will
find the PK file.

- To include your pictures in your document you have to tell TeX the font:
@example
  \\font\\gnufigs=myfigures
@end example

Each picture you made is stored in a single character.  The first picture is
character 0, the second is character 1, and so on...  After doing the above
step, you can use the pictures just like any other characters.  Therefore, to
place pictures 1 and 2 centered in your document, all you have to do is:
@example
  \\centerline@{\\gnufigs\\char0@}
  \\centerline@{\\gnufigs\\char1@}
@end example

in plain TeX.  For LaTeX you can, of course, use the picture environment and
place the picture wherever you wish by using the \\makebox and \\put macros.

This conversion saves you a lot of time once you have generated the font;
TeX handles the pictures as characters and uses minimal time to place them,
and the documents you make change more often than the pictures do.  It also
saves a lot of TeX memory.  One last advantage of using the METAFONT driver
is that the DVI file really remains device independent, because no \\special
commands are used as in the eepic and tpic drivers."

@node mp, mgr, mf, terminal_
@subsubsection mp

@c ?commands set terminal mpost
@c ?set terminal mp
@c ?set term mp
@c ?terminal mp
@c ?term mp
@cindex mp

@cindex metapost


The `mp` driver produces output intended to be input to the Metapost program.
Running Metapost on the file creates EPS files containing the plots. By
default, Metapost passes all text through TeX.  This has the advantage of
allowing essentially  any TeX symbols in titles and labels.

Syntax:
@example
   set term mp @{color | colour | monochrome@}
               @{solid | dashed@}
               @{notex | tex | latex@}
               @{magnification <magsize>@}
               @{psnfss | psnfss-version7 | nopsnfss@}
               @{prologues <value>@}
               @{a4paper@}
               @{amstex@}
               @{"<fontname>"@} @{<fontsize>@}

@end example

The option `color` causes lines to be drawn in color (on a printer or display
that supports it), `monochrome` (or nothing) selects black lines.  The option
`solid` draws solid lines, while `dashed` (or nothing) selects lines with
different patterns of dashes.  If `solid` is selected but `color` is not,
nearly all lines will be identical.  This may occasionally be useful, so it is
allowed.

The option `notex` bypasses TeX entirely, therefore no TeX code can be used in
labels under this option.  This is intended for use on old plot files or files
that make frequent use of common characters like `$` and `%` that require
special handling in TeX.

The option `tex` sets the terminal to output its text for TeX to process.

The option `latex` sets the terminal to output its text for processing by
LaTeX. This allows things like \\frac for fractions which LaTeX knows about
but TeX does not.  Note that you must set the environment variable TEX to the
name of your LaTeX executable (normally latex) if you use this option or use
`mpost --tex=<name of LaTeX executable> ...`. Otherwise metapost will try and
use TeX to process the text and it won't work.

Changing font sizes in TeX has no effect on the size of mathematics, and there
is no foolproof way to make such a change, except by globally  setting a
magnification factor. This is the purpose of the `magnification` option. It
must be followed by a scaling factor. All text (NOT the graphs) will be scaled
by this factor. Use this if you have math that you want at some size other
than the default 10pt. Unfortunately, all math will be the same size, but see
the discussion below on editing the MP output. `mag` will also work under
`notex` but there seems no point in using it as the font size option (below)
works as well.

The option `psnfss` uses postscript fonts in combination with LaTeX. Since
this option only makes sense, if LaTeX is being used, the `latex` option is selected
automatically. This option includes the following packages for LaTeX:
inputenc(latin1), fontenc(T1), mathptmx, helvet(scaled=09.2), courier, latexsym 
and textcomp.

The option `psnfss-version7` uses also postscript fonts in LaTeX (option `latex`
is also automatically selected), but uses the following packages with LaTeX:
inputenc(latin1), fontenc(T1), times, mathptmx, helvet and courier.

The option `nopsnfss` is the default and uses the standard font (cmr10 if not
otherwise specified).

The option `prologues` takes a value as an additional argument and adds the line
`prologues:=<value>` to the metapost file. If a value of `2` is specified metapost
uses postscript fonts to generate the eps-file, so that the result can be viewed
using e.g. ghostscript. Normally the output of metapost uses TeX fonts and therefore
has to be included in a (La)TeX file before you can look at it.

The option `noprologues` is the default. No additional line specifying the prologue
will be added.

The option `a4paper` adds a `[a4paper]` to the documentclass. Normally letter paper
is used (default). Since this option is only used in case of LaTeX, the `latex` option
is selected automatically.

The option `amstex` automatically selects the `latex` option and includes the following
LaTeX packages: amsfonts, amsmath(intlimits). By default these packages are not
included.

A name in quotes selects the font that will be used when no explicit font is
given in a @ref{label} or @ref{title}.  A name recognized by TeX (a TFM file
exists) must be used.  The default is "cmr10" unless `notex` is selected,
then it is "pcrr8r" (Courier).  Even under `notex`, a TFM file is needed by
Metapost. The file `pcrr8r.tfm` is the name given to Courier in LaTeX's psnfss
package.  If you change the font from the `notex` default, choose a font that
matches the ASCII encoding at least in the range 32-126.  `cmtt10` almost
works, but it has a nonblank character in position 32 (space).

The size can be any number between 5.0 and 99.99.  If it is omitted, 10.0 is
used.  It is advisable to use `magstep` sizes: 10 times an integer or
half-integer power of 1.2, rounded to two decimals, because those are the most
available sizes of fonts in TeX systems.

All the options are optional.  If font information is given, it must be at the
end, with size (if present) last.  The size is needed to select a size for the
font, even if the font name includes size information.  For example,
`set term mp "cmtt12"` selects cmtt12 shrunk to the default size 10.  This
is probably not what you want or you would have used cmtt10.

The following common ascii characters need special treatment in TeX:
@example
   $, &, #, %, _;  |, <, >;  ^, ~,  \\, @{, and @}
@end example

The five characters $, #, &, _, and % can simply be escaped, e.g., `\\$`.
The three characters <, >, and | can be wrapped in math mode, e.g., `$<$`.
The remainder require some TeX work-arounds.  Any good book on TeX will give
some guidance.

If you type your labels inside double quotes, backslashes in TeX code need to
be escaped (doubled). Using single quotes will avoid having to do this, but
then you cannot use `\\n` for line breaks.  As of this writing, version 3.7 of
gnuplot processes titles given in a `plot` command differently than in other
places, and backslashes in TeX commands need to be doubled regardless of the
style of quotes.

Metapost pictures are typically used in TeX documents.  Metapost deals with
fonts pretty much the same way TeX does, which is different from most other
document preparation programs.  If the picture is included in a LaTeX document
using the graphics package, or in a plainTeX document via epsf.tex, and then
converted to PostScript with dvips (or other dvi-to-ps converter), the text in
the plot will usually be handled correctly.  However, the text may not appear
if you send the Metapost output as-is to a PostScript interpreter.



@noindent --- METAPOST INSTRUCTIONS ---

@c ?commands set terminal mp detailed
@c ?set terminal mp detailed
@c ?set term mp detailed
@c ?mp detailed
@c ?metapost detailed

- Set your terminal to Metapost, e.g.:
@example
   set terminal mp mono "cmtt12" 12

@end example

- Select an output-file, e.g.:
@example
   set output "figure.mp"

@end example

- Create your pictures.  Each plot (or multiplot group) will generate a
separate Metapost beginfig...endfig group.  Its default size will be 5 by 3
inches.  You can change the size by saying `set size 0.5,0.5` or whatever
fraction of the default size you want to have.

- Quit gnuplot.

- Generate EPS files by running Metapost on the output of gnuplot:
@example
   mpost figure.mp  OR  mp figure.mp
@end example

The name of the Metapost program depends on the system, typically `mpost` for
a Unix machine and `mp` on many others.  Metapost will generate one EPS file
for each picture.

- To include your pictures in your document you can use the graphics package
in LaTeX or epsf.tex in plainTeX:
@example
   \\usepackage@{graphics@} % LaTeX
   \\input epsf.tex       % plainTeX
@end example

If you use a driver other than dvips for converting TeX DVI output to PS, you
may need to add the following line in your LaTeX document:
@example
   \\DeclareGraphicsRule@{*@}@{eps@}@{*@}@{@}
@end example

Each picture you made is in a separate file.  The first picture is in, e.g.,
figure.0, the second in figure.1, and so on....  To place the third picture in
your document, for example, all you have to do is:
@example
   \\includegraphics@{figure.2@} % LaTeX
   \\epsfbox@{figure.2@}         % plainTeX

@end example

The advantage, if any, of the mp terminal over a postscript terminal is
editable output.  Considerable effort went into making this output as clean as
possible.  For those knowledgeable in the Metapost language, the default line
types and colors can be changed by editing the arrays `lt[]` and `col[]`.
The choice of solid vs dashed lines, and color vs black lines can be change by
changing the values assigned to the booleans `dashedlines` and `colorlines`.
If the default `tex` option was in effect, global changes to the text of
labels can be achieved by editing the `vebatimtex...etex` block.  In
particular, a LaTeX preamble can be added if desired, and then LaTeX's
built-in size changing commands can be used for maximum flexibility. Be sure
to set the appropriate MP configuration variable to force Metapost to run
LaTeX instead of plainTeX."

@node mgr, mif, mp, terminal_
@subsubsection mgr

@c ?commands set terminal mgr
@c ?set terminal mgr
@c ?set term mgr
@c ?terminal mgr
@c ?term mgr
@cindex mgr
@tmindex mgr


The `mgr` terminal driver supports the Mgr Window system.  It has no options."

@node mif, mtos, mgr, terminal_
@subsubsection mif

@c ?commands set terminal mif
@c ?set terminal mif
@c ?set term mif
@c ?terminal mif
@c ?term mif
@cindex mif
@tmindex mif


The `mif` terminal driver produces Frame Maker MIF format version 3.00.  It
plots in MIF Frames with the size 15*10 cm, and plot primitives with the same
pen will be grouped in the same MIF group.  Plot primitives in a `gnuplot`
page will be plotted in a MIF Frame, and several MIF Frames are collected in
one large MIF Frame.  The MIF font used for text is "Times".

Several options may be set in the MIF 3.00 driver.

Syntax:
@example
      set terminal mif @{color | colour | monochrome@} @{polyline | vectors@}
                       @{help | ?@}

@end example

`colour` plots lines with line types >= 0 in colour (MIF sep. 2--7) and
`monochrome` plots all line types in black (MIF sep. 0).
`polyline` plots curves as continuous curves and `vectors` plots curves as
collections of vectors.
@ref{help} and `?` print online help on standard error output---both print a
short description of the usage; @ref{help} also lists the options.

Examples:
@example
      set term mif colour polylines    # defaults
      set term mif                     # defaults
      set term mif vectors
      set term mif help"

@end example

@node mtos, next, mif, terminal_
@subsubsection mtos

@c ?commands set terminal mtos
@c ?set terminal mtos
@c ?set term mtos
@c ?terminal mtos
@c ?term mtos
@cindex mtos
@tmindex mtos


The `mtos` terminal has no options.  It sends data via a pipe to an external
program called GPCLIENT.  It runs under MULTITOS, Magic 3.x, MagicMAC. and
MiNT.  If you cannot find GPCLIENT, than mail to dirk@@lstm.uni-erlangen.de."

@node next, Openstep_(next), mtos, terminal_
@subsubsection next

@c ?commands set terminal next
@c ?set terminal next
@c ?set term next
@c ?terminal next
@c ?term next
@cindex next

@cindex NeXT

Several options may be set in the next driver.

Syntax:
@example
      set terminal next @{<mode>@} @{<type> @} @{<color>@} @{<dashed>@}
                 @{"<fontname>"@} @{<fontsize>@} title @{"<newtitle>"@}

@end example

where <mode> is  `default`, which sets all options to their defaults;
<type> is either `new` or `old`, where `old` invokes the old single window;
<color> is either `color` or `monochrome`;
<dashed> is either `solid` or `dashed`;
"<fontname>" is the name of a valid PostScript font;
<fontsize> is the size of the font in PostScript points; and
<title> is the title for the GnuTerm window.
Defaults are  `new`, `monochrome`, `dashed`, "Helvetica", 14pt.

Examples:
@example
      set term next default
      set term next 22
      set term next color "Times-Roman" 14
      set term next color "Helvetica" 12 title "MyPlot"
      set term next old

@end example

Pointsizes may be changed with `set linestyle`."

@node Openstep_(next), pbm, next, terminal_
@subsubsection Openstep (next)

@c ?commands set terminal openstep
@c ?set terminal openstep
@c ?set term openstep
@c ?terminal openstep
@c ?term openstep
@cindex openstep

@cindex OpenStep

@cindex Openstep

/*
@cindex next

@cindex NeXT

*/
Several options may be set in the openstep (next) driver.

Syntax:
@example
      set terminal openstep @{<mode>@} @{<type> @} @{<color>@} @{<dashed>@}
                 @{"<fontname>"@} @{<fontsize>@} title @{"<newtitle>"@}

@end example

where <mode> is  `default`, which sets all options to their defaults;
<type> is either `new` or `old`, where `old` invokes the old single window;
<color> is either `color` or `monochrome`;
<dashed> is either `solid` or `dashed`;
"<fontname>" is the name of a valid PostScript font;
<fontsize> is the size of the font in PostScript points; and
<title> is the title for the GnuTerm window.
Defaults are  `new`, `monochrome`, `dashed`, "Helvetica", 14pt.

Examples:
@example
      set term openstep default
      set term openstep 22
      set term openstep color "Times-Roman" 14
      set term openstep color "Helvetica" 12 title "MyPlot"
      set term openstep old

@end example

Pointsizes may be changed with `set linestyle`."

@node pbm, dospc, Openstep_(next), terminal_
@subsubsection pbm

@c ?commands set terminal pbm
@c ?set terminal pbm
@c ?set term pbm
@c ?terminal pbm
@c ?term pbm
@cindex pbm
@tmindex pbm


Several options may be set in the `pbm` terminal---the driver for PBMplus.

Syntax:
@example
      set terminal pbm @{<fontsize>@} @{<mode>@} @{size <x>,<y>@}

@end example

where <fontsize> is `small`, `medium`, or `large` and <mode> is `monochrome`,
`gray` or `color`.  The default plot size is 640 pixels wide and 480 pixels
high.

The output of the `pbm` driver depends upon <mode>: `monochrome` produces a
portable bitmap (one bit per pixel), `gray` a portable graymap (three bits
per pixel) and `color` a portable pixmap (color, four bits per pixel).

The output of this driver can be used with various image conversion and
manipulation utilities provided by NETPBM.  Based on Jef Poskanzer's
PBMPLUS package, NETPBM provides programs to convert the above PBM formats
to GIF, TIFF, MacPaint, Macintosh PICT, PCX, X11 bitmap and many others.
Complete information is available at http://netpbm.sourceforge.net/.

Examples:
@example
      set terminal pbm small monochrome                # defaults
      set terminal pbm color medium size 800,600
      set output '| pnmrotate 45 | pnmtopng > tilted.png'  # uses NETPBM"

@end example

@node dospc, pdf, pbm, terminal_
@subsubsection dospc

@c ?commands set terminal dospc
@c ?set terminal dospc
@c ?set term dospc
@c ?terminal dospc
@c ?term dospc
@cindex dospc
@tmindex dospc


The `dospc` terminal driver supports PCs with arbitrary graphics boards,
which will be automatically detected.  It should be used only if you are
not using the gcc or Zortec C/C++ compilers."

@node pdf, pstricks, dospc, terminal_
@subsubsection pdf

@c ?commands set terminal pdf
@c ?set terminal pdf
@c ?set term pdf
@c ?terminal pdf
@c ?term pdf
@cindex pdf
@tmindex pdf


This terminal produces files in the Adobe Portable Document Format
(PDF), useable for printing or display with tools like Acrobat Reader

Syntax:
@example
      set terminal pdf @{monochrome|color|colour@}
                       @{@{no@}enhanced@}
                       @{fname "<font>"@} @{fsize <fontsize>@}
                       @{font "<fontname>@{,<fontsize>@}"@}
                       @{linewidth <lw>@} @{rounded|butt@}
                       @{solid|dashed@} @{dl <dashlength>@}@}
                       @{size <XX>@{unit@},<YY>@{unit@}@}

@end example

The default is to use a different color for each line type. Selecting
`monochome` will use black for all linetypes, in which case you probably
want to select `dashed` to distinguish line types. Even in in mono mode
you can still use explicit colors for filled areas or linestyles.

where <font> is the name of the default font to use (default Helvetica)
and <fontsize> is the font size (in points, default 12).
For help on which fonts are available or how to install new ones, please
see the documentation for your local installation of pdflib.

The `enhanced` option enables enhanced text processing features
(subscripts, superscripts and mixed fonts). See `enhanced`.

The width of all lines in the plot can be increased by the factor <n>
specified in `linewidth`. Similarly `dashlength` is a multiplier for the
default dash spacing.

`rounded` sets line caps and line joins to be rounded; `butt` is the
default, butt caps and mitered joins.

The default size for PDF output is 5 inches by 3 inches. The @ref{size} option
changes this to whatever the user requests. By default the X and Y sizes
are taken to be in inches, but other units are possible (currently only cm).

* does not work.

@node pstricks, qms, pdf, terminal_
@subsubsection pstricks

@c ?commands set terminal pstricks
@c ?set terminal pstricks
@c ?set term pstricks
@c ?terminal pstricks
@c ?term pstricks
@cindex pstricks
@tmindex pstricks


The `pstricks` driver is intended for use with the "pstricks.sty" macro
package for LaTeX.  It is an alternative to the `eepic` and `latex` drivers.
You need "pstricks.sty", and, of course, a printer that understands
PostScript, or a converter such as Ghostscript.

PSTricks is available via anonymous ftp from the /pub directory at
Princeton.edu.  This driver definitely does not come close to using the full
capability of the PSTricks package.

Syntax:
@example
      set terminal pstricks @{hacktext | nohacktext@} @{unit | nounit@}

@end example

The first option invokes an ugly hack that gives nicer numbers; the second
has to do with plot scaling.  The defaults are `hacktext` and `nounit`."

@node qms, regis, pstricks, terminal_
@subsubsection qms

@c ?commands set terminal qms
@c ?set terminal qms
@c ?set term qms
@c ?terminal qms
@c ?term qms
@cindex qms
@tmindex qms


The `qms` terminal driver supports the QMS/QUIC Laser printer, the Talaris
1200 and others.  It has no options."

@node regis, regis_, qms, terminal_
@subsubsection regis

@c ?commands set terminal regis
@c ?set terminal regis
@c ?set term regis
@c ?terminal regis
@c ?term regis
@cindex regis
@tmindex regis


The `regis` terminal device generates output in the REGIS graphics language.
It has the option of using 4 (the default) or 16 colors.

Syntax:
@example
      set terminal regis @{4 | 16@}"

@end example

@node regis_, rgip, regis, terminal_
@subsubsection regis

@c ?commands set terminal regis
@c ?set terminal regis
@c ?set term regis
@c ?terminal regis
@c ?term regis
@cindex regis
@tmindex regis


The `regis` terminal device generates output in the REGIS graphics language.
It has the option of using 4 (the default) or 16 colors.

Syntax:
@example
      set terminal regis @{4 | 16@}"

@end example

@node rgip, sun, regis_, terminal_
@subsubsection rgip

@c ?commands set terminal rgip
@c ?set terminal rgip
@c ?set term rgip
@c ?terminal rgip
@c ?term rgip
@cindex rgip
@tmindex rgip


@c ?commands set terminal uniplex
@c ?set terminal uniplex
@c ?set term uniplex
@c ?terminal uniplex
@c ?term uniplex
@cindex uniplex
@tmindex uniplex


The `rgip` and `uniplex` terminal drivers support RGIP metafiles.  They can
combine several graphs on a single page, but only one page is allowed in a
given output file.

Syntax:
@example
      set terminal rgip | uniplex @{portrait | landscape@}
                                  @{[<horiz>,<vert>]@} @{<fontsize>@}

@end example

permissible values for the font size are in the range 1--8, with the default
being 1.  The default layout is landscape.  Graphs are placed on the page in
a `horiz`x`vert` grid, which defaults to [1,1].

Example:
@example
      set terminal uniplex portrait [2,3]

@end example

puts six graphs on a page in three rows of two in portrait orientation."

@node sun, svg, rgip, terminal_
@subsubsection sun

@c ?commands set terminal sun
@c ?set terminal sun
@c ?set term sun
@c ?terminal sun
@c ?term sun
@cindex sun
@tmindex sun


The `sun` terminal driver supports the SunView window system.  It has no
options."

@node svg, tek410x, sun, terminal_
@subsubsection svg

@c ?commands set terminal svg
@c ?set terminal svg
@c ?set term svg
@c ?terminal svg
@c ?term svg
@cindex svg
@tmindex svg


This terminal produces files in the W3C Scalable Vector Graphics format.

Syntax:
@example
      set terminal svg @{size <x>,<y> @{|fixed|dynamic@}@}
                       @{@{no@}enhanced@}
                       @{fname "<font>"@} @{fsize <fontsize>@}
                       @{font "<fontname>@{,<fontsize>@}"@}
                       @{fontfile <filename>@}
                       @{rounded|butt@} @{solid|dashed@} @{linewidth <lw>@}

@end example

where <x> and <y> are the size of the SVG plot to generate,
`dynamic` allows a svg-viewer to resize plot, whereas the default
setting, `fixed`, will request an absolute size.

`linewidth <w>` increases the width of all lines used in the figure
by a factor of <w>.

<font> is the name of the default font to use (default Arial) and
<fontsize> is the font size (in points, default 12). SVG viewing
programs may substitute other fonts when the file is displayed.

The svg terminal supports an enhanced text mode, which allows font
and other formatting commands to be embedded in labels and other text
strings. The enhanced text mode syntax is shared with other gnuplot
terminal types. See `enhanced` for more details.

SVG allows you to embed fonts directly into an SVG document, or to
provide a hypertext link to the desired font. The `fontfile` option
specifies a local file which is copied into the <defs> section of the
resulting SVG output file.  This file may either itself contain a font,
or may contain the records necessary to create a hypertext reference to
the desired font. Gnuplot will look for the requested file using the
directory list in the GNUPLOT_FONTPATH environmental variable.
NB: You must embed an svg font, not a TrueType or PostScript font."

@node tek410x, tek410x_, svg, terminal_
@subsubsection tek410x

@c ?commands set terminal tek410x
@c ?set terminal tek410x
@c ?set term tek410x
@c ?terminal tek410x
@c ?term tek410x
@cindex tek410x
@tmindex tek410x


The `tek410x` terminal driver supports the 410x and 420x family of Tektronix
terminals.  It has no options."

@node tek410x_, tek40, tek410x, terminal_
@subsubsection tek410x

@c ?commands set terminal tek410x
@c ?set terminal tek410x
@c ?set term tek410x
@c ?terminal tek410x
@c ?term tek410x
@cindex tek410x
@tmindex tek410x


The `tek410x` terminal driver supports the 410x and 420x family of Tektronix
terminals.  It has no options."

@node tek40, texdraw, tek410x_, terminal_
@subsubsection tek40

@c ?commands set terminal tek40xx
@c ?set terminal tek40xx
@c ?set term tek40xx
@c ?terminal tek40xx
@c ?term tek40xx
@cindex tek40
@tmindex tek40


@c ?commands set terminal vttek
@c ?set terminal vttek
@c ?set term vttek
@c ?terminal vttek
@c ?term vttek
@cindex vttek
@tmindex vttek


@c ?commands set terminal kc-tek40xx
@c ?set terminal kc-tek40xx
@c ?set term kc-tek40xx
@c ?terminal kc-tek40xx
@c ?term kc-tek40xx
@cindex kc-tek40xx
@tmindex kc-tek40xx


@c ?commands set terminal km-tek40xx
@c ?set terminal km-tek40xx
@c ?set term km-tek40xx
@c ?terminal km-tek40xx
@c ?term km-tek40xx
@cindex km-tek40xx
@tmindex km-tek40xx


@c ?commands set terminal selanar
@c ?set terminal selanar
@c ?set term selanar
@c ?terminal selanar
@c ?term selanar
@cindex selanar
@tmindex selanar


@c ?commands set terminal bitgraph
@c ?set terminal bitgraph
@c ?set term bitgraph
@c ?terminal bitgraph
@c ?term bitgraph
@cindex bitgraph
@tmindex bitgraph


@c ?commands set terminal xterm
@c ?set terminal xterm
@c ?set term xterm
@c ?terminal xterm
@c ?term xterm
@cindex xterm
@tmindex xterm


This family of terminal drivers supports a variety of VT-like terminals.
`tek40xx` supports Tektronix 4010 and others as well as most TEK emulators;
`vttek` supports VT-like tek40xx terminal emulators; `kc-tek40xx` supports
MS-DOS Kermit Tek4010 terminal emulators in color: `km-tek40xx` supports them
in monochrome; `selanar` supports Selanar graphics; and `bitgraph` supports
BBN Bitgraph terminals.  None have any options."

@node texdraw, tgif, tek40, terminal_
@subsubsection texdraw

@c ?commands set terminal texdraw
@c ?set terminal texdraw
@c ?set term texdraw
@c ?terminal texdraw
@c ?term texdraw
@cindex texdraw
@tmindex texdraw


The `texdraw` terminal driver supports the LaTeX texdraw environment.  It is
intended for use with "texdraw.sty" and "texdraw.tex" in the texdraw package.

Points, among other things, are drawn using the LaTeX commands "\\Diamond" and
"\\Box".  These commands no longer belong to the LaTeX2e core; they are included
in the latexsym package, which is part of the base distribution and thus part
of any LaTeX implementation.  Please do not forget to use this package.

It has no options."

@node tgif, tgif_, texdraw, terminal_
@subsubsection tgif

@c ?commands set terminal tgif
@c ?set terminal tgif
@c ?set term tgif
@c ?terminal tgif
@c ?term tgif
@cindex tgif
@tmindex tgif


Tgif is an X11-based drawing tool---it has nothing to do with GIF.

The `tgif` driver supports different pointsizes (with @ref{pointsize}),
different label fonts and font sizes (e.g. `set label "Hallo" at x,y font
"Helvetica,34"`) and multiple graphs on the page.  The proportions of the
axes are not changed.

Syntax:
@example
      set terminal tgif @{portrait | landscape | default@} @{<[x,y]>@}
                        @{monochrome | color@}
                        @{@{linewidth | lw@} <LW>@}
                        @{solid | dashed@}
                        @{font "<fontname>"@} @{<fontsize>@}

@end example

where <[x,y]> specifies the number of graphs in the x and y directions on the
page, `color` enables color, `linewidth` scales all linewidths by <LW>,
"<fontname>" is the name of a valid PostScript font, and <fontsize>
specifies the size of the PostScript font.
`defaults` sets all options to their defaults: `portrait`, `[1,1]`, `color`,
`linwidth 1.0`, `dashed`, `"Helvetica"`, and `18`.

The `solid` option is usually prefered if lines are colored, as they often
are in the editor.  Hardcopy will be black-and-white, so `dashed` should be
chosen for that.

Multiplot is implemented in two different ways.

The first multiplot implementation is the standard gnuplot multiplot feature:

@example
      set terminal tgif
      set output "file.obj"
      set multiplot
      set origin x01,y01
      set size  xs,ys
      plot ...
           ...
      set origin x02,y02
      plot ...
      unset multiplot

@end example

See @ref{multiplot} for further information.

The second version is the [x,y] option for the driver itself.  The advantage
of this implementation is that everything is scaled and placed automatically
without the need for setting origins and sizes; the graphs keep their natural
x/y proportions of 3/2 (or whatever is fixed by @ref{size}).

If both multiplot methods are selected, the standard method is chosen and a
warning message is given.

Examples of single plots (or standard multiplot):
@example
      set terminal tgif                  # defaults
      set terminal tgif "Times-Roman" 24
      set terminal tgif landscape
      set terminal tgif landscape solid

@end example

Examples using the built-in multiplot mechanism:
@example
      set terminal tgif portrait [2,4]  # portrait; 2 plots in the x-
                                        # and 4 in the y-direction
      set terminal tgif [1,2]           # portrait; 1 plot in the x-
                                        # and 2 in the y-direction
      set terminal tgif landscape [3,3] # landscape; 3 plots in both
                                        # directions"

@end example

@node tgif_, tkcanvas, tgif, terminal_
@subsubsection tgif

@c ?commands set terminal tgif
@c ?set terminal tgif
@c ?set term tgif
@c ?terminal tgif
@c ?term tgif
@cindex tgif
@tmindex tgif


Tgif is an X11-based drawing tool---it has nothing to do with GIF.

The `tgif` driver supports different pointsizes (with @ref{pointsize}),
different label fonts and font sizes (e.g. `set label "Hallo" at x,y font
"Helvetica,34"`) and multiple graphs on the page.  The proportions of the
axes are not changed.

Syntax:
@example
      set terminal tgif @{portrait | landscape | default@} @{<[x,y]>@}
                        @{monochrome | color@}
                        @{@{linewidth | lw@} <LW>@}
                        @{solid | dashed@}
                        @{font "<fontname>"@} @{<fontsize>@}

@end example

where <[x,y]> specifies the number of graphs in the x and y directions on the
page, `color` enables color, `linewidth` scales all linewidths by <LW>,
"<fontname>" is the name of a valid PostScript font, and <fontsize>
specifies the size of the PostScript font.
`defaults` sets all options to their defaults: `portrait`, `[1,1]`, `color`,
`linwidth 1.0`, `dashed`, `"Helvetica"`, and `18`.

The `solid` option is usually prefered if lines are colored, as they often
are in the editor.  Hardcopy will be black-and-white, so `dashed` should be
chosen for that.

Multiplot is implemented in two different ways.

The first multiplot implementation is the standard gnuplot multiplot feature:

@example
      set terminal tgif
      set output "file.obj"
      set multiplot
      set origin x01,y01
      set size  xs,ys
      plot ...
           ...
      set origin x02,y02
      plot ...
      unset multiplot

@end example

See @ref{multiplot} for further information.

The second version is the [x,y] option for the driver itself.  The advantage
of this implementation is that everything is scaled and placed automatically
without the need for setting origins and sizes; the graphs keep their natural
x/y proportions of 3/2 (or whatever is fixed by @ref{size}).

If both multiplot methods are selected, the standard method is chosen and a
warning message is given.

Examples of single plots (or standard multiplot):
@example
      set terminal tgif                  # defaults
      set terminal tgif "Times-Roman" 24
      set terminal tgif landscape
      set terminal tgif landscape solid

@end example

Examples using the built-in multiplot mechanism:
@example
      set terminal tgif portrait [2,4]  # portrait; 2 plots in the x-
                                        # and 4 in the y-direction
      set terminal tgif [1,2]           # portrait; 1 plot in the x-
                                        # and 2 in the y-direction
      set terminal tgif landscape [3,3] # landscape; 3 plots in both
                                        # directions"

@end example

@node tkcanvas, tpic, tgif_, terminal_
@subsubsection tkcanvas

@c ?commands set terminal tkcanvas
@c ?set terminal tkcanvas
@c ?set term tkcanvas
@c ?terminal tkcanvas
@c ?term tkcanvas
@cindex tkcanvas
@tmindex tkcanvas


This terminal driver generates Tk canvas widget commands based on Tcl/Tk
(default) or Perl.  To use it, rebuild `gnuplot` (after uncommenting or
inserting the appropriate line in "term.h"), then

@example
 gnuplot> set term tkcanvas @{perltk@} @{interactive@}
 gnuplot> set output 'plot.file'

@end example

After invoking "wish", execute the following sequence of Tcl/Tk commands:

@example
 % source plot.file
 % canvas .c
 % pack .c
 % gnuplot .c

@end example

Or, for Perl/Tk use a program like this:

@example
 use Tk;
 my $top = MainWindow->new;
 my $c = $top->Canvas->pack;
 my $gnuplot = do "plot.pl";
 $gnuplot->($c);
 MainLoop;

@end example

The code generated by `gnuplot` creates a procedure called "gnuplot"
that takes the name of a canvas as its argument.  When the procedure is
called, it clears the canvas, finds the size of the canvas and draws the plot
in it, scaled to fit.

For 2-dimensional plotting (`plot`) two additional procedures are defined:
"gnuplot_plotarea" will return a list containing the borders of the plotting
area "xleft, xright, ytop, ybot" in canvas screen coordinates, while the ranges
of the two axes "x1min, x1max, y1min, y1max, x2min, x2max, y2min, y2max" in plot
coordinates can be obtained calling "gnuplot_axisranges".
If the "interactive" option is specified, mouse clicking on a line segment
will print the coordinates of its midpoint to stdout. Advanced actions
can happen instead if the user supplies a procedure named
"user_gnuplot_coordinates", which takes the following arguments:
"win id x1s y1s x2s y2s x1e y1e x2e y2e x1m y1m x2m y2m",
the name of the canvas and the id of the line segment followed by the
coordinates of its start and end point in the two possible axis ranges; the
coordinates of the midpoint are only filled for logarithmic axes.

The current version of `tkcanvas` supports neither @ref{multiplot} nor @ref{replot}."

@node tpic, unixpc, tkcanvas, terminal_
@subsubsection tpic

@c ?commands set terminal tpic
@c ?set terminal tpic
@c ?set term tpic
@c ?terminal tpic
@c ?term tpic
@cindex tpic
@tmindex tpic


The `tpic` terminal driver supports the LaTeX picture environment with tpic
\\specials.  It is an alternative to the `latex` and `eepic` terminal drivers.
Options are the point size, line width, and dot-dash interval.

Syntax:
@example
      set terminal tpic <pointsize> <linewidth> <interval>

@end example

where @ref{pointsize} and `linewidth` are integers in milli-inches and `interval`
is a float in inches.  If a non-positive value is specified, the default is
chosen: pointsize = 40, linewidth = 6, interval = 0.1.

All drivers for LaTeX offer a special way of controlling text positioning:
If any text string begins with '@{', you also need to include a '@}' at the
end of the text, and the whole text will be centered both horizontally
and vertically by LaTeX. --- If the text string begins with '[', you need
to continue it with: a position specification (up to two out of t,b,l,r),
']@{', the text itself, and finally, '@}'. The text itself may be anything
LaTeX can typeset as an LR-box. \\rule@{@}@{@}'s may help for best positioning.

Examples:
About label positioning:
Use gnuplot defaults (mostly sensible, but sometimes not really best):
@example
       set title '\\LaTeX\\ -- $ \\gamma $'
@end example

Force centering both horizontally and vertically:
@example
       set label '@{\\LaTeX\\ -- $ \\gamma $@}' at 0,0
@end example

Specify own positioning (top here):
@example
       set xlabel '[t]@{\\LaTeX\\ -- $ \\gamma $@}'
@end example

The other label -- account for long ticlabels:
@example
       set ylabel '[r]@{\\LaTeX\\ -- $ \\gamma $\\rule@{7mm@}@{0pt@}@}'"

@end example

@node unixpc, unixplot, tpic, terminal_
@subsubsection unixpc

@c ?commands set terminal unixpc
@c ?set terminal unixpc
@c ?set term unixpc
@c ?terminal unixpc
@c ?term unixpc
@cindex unixpc
@tmindex unixpc


The `unixpc` terminal driver supports AT&T 3b1 and AT&T 7300 Unix PC.  It has
no options."

@node unixplot, vx384, unixpc, terminal_
@subsubsection unixplot

@c ?commands set terminal unixplot
@c ?set terminal unixplot
@c ?set term unixplot
@c ?terminal unixplot
@c ?term unixplot
@cindex unixplot
@tmindex unixplot


The `unixplot` terminal driver generates output in the Unix "plot" graphics
language.  It has no options.

This terminal cannot be compiled if the GNU version of plot is to be used;
in that case, use the `gnugraph` terminal instead."

@node vx384, vgagl, unixplot, terminal_
@subsubsection vx384

@c ?commands set terminal vx384
@c ?set terminal vx384
@c ?set term vx384
@c ?terminal vx384
@c ?term vx384
@cindex vx384
@tmindex vx384


The `vx384` terminal driver supports the Vectrix 384 and Tandy color
printers.  It has no options."

@node vgagl, VWS, vx384, terminal_
@subsubsection vgagl

@c ?commands set terminal vgagl
@c ?set terminal vgagl
@c ?set term vgagl
@c ?terminal vgagl
@c ?term vgagl
@cindex vgagl
@tmindex vgagl


The `vgagl` driver is a fast linux console driver with full mouse and pm3d
support.  It looks at the environment variable SVGALIB_DEFAULT_MODE for the
default mode; if not set, it uses a 256 color mode with the highest
available resolution.

Syntax:
@example
   set terminal vgagl \\
                background [red] [[green] [blue]] \\
                [uniform | interpolate] \\
                [dump "file"] \\
                [mode]

@end example

The color mode can also be given with the mode option. Both Symbolic
names as G1024x768x256 and integers are allowed. The `background` option
takes either one or three integers in the range [0, 255]. If only one
integers is supplied, it is taken as gray value for the background.
If three integers are present, the background gets the corresponding
color.
The (mutually exclusive) options `interpolate` and `uniform` control
if color interpolation is done while drawing triangles (on by default).

A @ref{file} can be specified with the `dump "file"` option.
If this option is present, (i.e the dump file name is not empty) pressing
the key KP_Delete will write the file.  This action cannot and cannot be
rebound. The file is written in raw ppm (P6) format. Note that this option
is reset each time the `set term` command is issued.

To get high resolution modes, you will probably have to modify the
configuration file of libvga, usually /etc/vga/libvga.conf.  Using
the VESA fb is a good choice, but this needs to be compiled in the
kernel.

The vgagl driver uses the first *available* vga mode from the following list:
@example
 - the driver which was supplied when setting vgagl, e.g. `set term vgagl
   G1024x768x256` would first check, if the G1024x768x256 mode is available.
 - the environment variable SVGALIB_DEFAULT_MODE
 - G1024x768x256
 - G800x600x256
 - G640x480x256
 - G320x200x256
 - G1280x1024x256
 - G1152x864x256
 - G1360x768x256
 - G1600x1200x256

@end example


@node VWS, windows, vgagl, terminal_
@subsubsection VWS

@c ?commands set terminal VWS
@c ?set terminal VWS
@c ?set term VWS
@c ?terminal VWS
@c ?term VWS
@cindex VWS
@tmindex VWS


The `VWS` terminal driver supports the VAX Windowing System.  It has
no options.  It will sense the display type (monochrome, gray scale,
or color.)  All line styles are plotted as solid lines."

@node windows, x11, VWS, terminal_
@subsubsection windows

@c ?commands set terminal windows
@c ?set terminal windows
@c ?set term windows
@c ?terminal windows
@c ?term windows
@cindex windows
@tmindex windows


Three options may be set in the `windows` terminal driver.

Syntax:
@example
      set terminal windows @{color | monochrome@}
                           @{enhanced | noenhanced@}
                           @{@{font@} "fontname@{,fontsize@}" @{<fontsize>@}@}

@end example

where `color` and `monochrome` select colored or mono output,
`enhanced` enables enhanced text mode features (subscripts,
superscripts and mixed fonts). See `enhanced` for more information.
`"<fontname>"` is the name of a valid Windows font, and `<fontsize>`
is the size of the font in points.

Other options may be set with the graph-menu or the initialization file.

The Windows version normally terminates immediately as soon as the end of
any files given as command line arguments is reached (i.e. in non-interactive
mode), unless you specify `-` as the last command line option.
It will also not show the text-window at all, in this mode, only the plot.
By giving the optional argument `-persist` (same as for gnuplot under x11;
former Windows-only options `/noend` or `-noend` are still accepted as well),
will not close gnuplot. Contrary to gnuplot on other operating systems,
gnuplot's interactive command line is accessible after the -persist option.


@noindent --- GRAPH-MENU ---

@c ?commands set terminal windows graph-menu
@c ?set terminal windows graph-menu
@c ?set term windows graph-menu
@c ?windows graph-menu
@cindex graph-menu
@tmindex graph-menu


The `gnuplot graph` window has the following options on a pop-up menu
accessed by pressing the right mouse button or selecting `Options` from the
system menu:

`Bring to Top` when checked brings the graph window to the top after every
plot.

`Color` when checked enables color linestyles.  When unchecked it forces
monochrome linestyles.

`Copy to Clipboard` copies a bitmap and a Metafile picture.

`Background...` sets the window background color.

`Choose Font...` selects the font used in the graphics window.

`Line Styles...` allows customization of the line colors and styles.

`Print...` prints the graphics windows using a Windows printer driver and
allows selection of the printer and scaling of the output.  The output
produced by `Print` is not as good as that from `gnuplot`'s own printer
drivers.

`Update wgnuplot.ini` saves the current window locations, window sizes, text
window font, text window font size, graph window font, graph window font
size, background color and linestyles to the initialization file
`WGNUPLOT.INI`.


@noindent --- PRINTING ---

@c ?commands set terminal windows printing
@c ?set terminal windows printing
@c ?set term windows printing
@c ?windows printing
@cindex printing
@tmindex printing


In order of preference, graphs may be be printed in the following ways.

`1.` Use the `gnuplot` command @ref{terminal} to select a printer and @ref{output} to redirect output to a file.

`2.` Select the `Print...` command from the `gnuplot graph` window.  An extra
command `screendump` does this from the text window.

`3.` If `set output "PRN"` is used, output will go to a temporary file.  When
you exit from `gnuplot` or when you change the output with another @ref{output} command, a dialog box will appear for you to select a printer port.
If you choose OK, the output will be printed on the selected port, passing
unmodified through the print manager.  It is possible to accidentally (or
deliberately) send printer output meant for one printer to an incompatible
printer.


@noindent --- TEXT-MENU ---

@c ?commands set terminal windows text-menu
@c ?set terminal windows text-menu
@c ?set term windows text-menu
@c ?windows text-menu
@cindex text-menu
@tmindex text-menu


The `gnuplot text` window has the following options on a pop-up menu accessed
by pressing the right mouse button or selecting `Options` from the system
menu:

`Copy to Clipboard` copies marked text to the clipboard.

`Paste` copies text from the clipboard as if typed by the user.

`Choose Font...` selects the font used in the text window.

`System Colors` when selected makes the text window honor the System Colors
set using the Control Panel.  When unselected, text is black or blue on a
white background.

`Update wgnuplot.ini` saves the current text window location, text window
size, text window font and text window font size to the initialisation file
`WGNUPLOT.INI`.

`MENU BAR`

If the menu file `WGNUPLOT.MNU` is found in the same directory as
WGNUPLOT.EXE, then the menu specified in `WGNUPLOT.MNU` will be loaded.
Menu commands:

[Menu] starts a new menu with the name on the following line.

[EndMenu] ends the current menu.

[--] inserts a horizontal menu separator.

[|] inserts a vertical menu separator.

[Button] puts the next macro on a push button instead of a menu.

Macros take two lines with the macro name (menu entry) on the first line and
the macro on the second line.  Leading spaces are ignored.  Macro commands:

[INPUT] --- Input string with prompt terminated by [EOS] or @{ENTER@}

[EOS] --- End Of String terminator.  Generates no output.

[OPEN] --- Get name of file to open from list box, with title of list box
terminated by [EOS], followed by default filename terminated by [EOS] or
@{ENTER@}.

[SAVE] --- Get name of file to save.  Similar to [OPEN]

Macro character substitutions:

@{ENTER@} --- Carriage Return '\\r'

@{TAB@} --- Tab '\\011'

@{ESC@} --- Escape '\\033'

@{^A@} --- '\\001'

...

@{^_@} --- '\\031'

Macros are limited to 256 characters after expansion.


@noindent --- WGNUPLOT.INI ---

@c ?commands set terminal windows wgnuplot.ini
@c ?set terminal windows wgnuplot.ini
@c ?set term windows wgnuplot.ini
@c ?windows wgnuplot.ini
@cindex wgnuplot.ini
@tmindex wgnuplot.ini


Windows `gnuplot` will read some of its options from the `[WGNUPLOT]` section
of `WGNUPLOT.INI` in user's %APPDATA% directory.  A sample `WGNUPLOT.INI` file:

@example
      [WGNUPLOT]
      TextOrigin=0 0
      TextSize=640 150
      TextFont=Terminal,9
      GraphOrigin=0 150
      GraphSize=640 330
      GraphFont=Arial,10
      GraphColor=1
      GraphToTop=1
      GraphBackground=255 255 255
      Border=0 0 0 0 0
      Axis=192 192 192 2 2
      Line1=0 0 255 0 0
      Line2=0 255 0 0 1
      Line3=255 0 0 0 2
      Line4=255 0 255 0 3
      Line5=0 0 128 0 4

@end example

The `GraphFont` entry specifies the font name and size in points.  The five
numbers given in the `Border`, `Axis` and `Line` entries are the `Red`
intensity (0--255), `Green` intensity, `Blue` intensity, `Color Linestyle`
and `Mono Linestyle`.  `Linestyles` are 0=SOLID, 1=DASH, 2=DOT, 3=DASHDOT,
4=DASHDOTDOT.  In the sample `WGNUPLOT.INI` file above, Line 2 is a green
solid line in color mode, or a dashed line in monochrome mode.  The default
line width is 1 pixel.  If `Linestyle` is negative, it specifies the width of
a SOLID line in pixels.  Line1 and any linestyle used with the `points` style
must be SOLID with unit width."

@node x11, x11_, windows, terminal_
@subsubsection x11

@c ?commands set terminal x11
@c ?set terminal x11
@c ?set term x11
@c ?terminal x11
@c ?term x11
@cindex x11

@cindex X11

`gnuplot` provides the `x11` terminal type for use with X servers.  This
terminal type is set automatically at startup if the `DISPLAY` environment
variable is set, if the `TERM` environment variable is set to `xterm`, or
if the `-display` command line option is used.

Syntax:
@example
   set terminal x11 @{<n>@}
                    @{title "<string>"@}
                    @{@{no@}enhanced@} @{font <fontspec>@}
                    @{linewidth LW@} @{solid|dashed@}
                    @{@{no@}persist@} @{@{no@}raise@} @{@{no@}ctrlq@}
                    @{close@}
                    @{size XX,YY@} @{position XX,YY@}
   set terminal x11 @{reset@}

@end example

Multiple plot windows are supported: `set terminal x11 <n>` directs the
output to plot window number n.  If n is not 0, the terminal number will be
appended to the window title (unless a title has been supplied manually)
and the icon will be labeled `Gnuplot <n>`.  The active window may be
distinguished by a change in cursor (from default to crosshair).

The x11 terminal support enhanced text mode (see `enhanced`), subject
to the available fonts. In order for font size commands embedded in text
to have any effect, the default x11 font must be scalable. Thus the first
example below will work as expected, but the second will not.

@example
   set term x11 enhanced font "arial,15" 
   set title '@{/=20 Big@} Medium @{/=5 Small@}' 

@end example

@example
   set term x11 enhanced font "terminal-14" 
   set title '@{/=20 Big@} Medium @{/=5 Small@}' 

@end example

Plot windows remain open even when the `gnuplot` driver is changed to a
different device.  A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing `close` from a window
manager menu.  All plot windows can be closed by specifying @ref{reset}, which
actually terminates the subprocess which maintains the windows (unless
`-persist` was specified).  The `close` command can be used to close
individual plot windows by number.  However, after a @ref{reset}, those plot
windows left due to persist cannot be closed with the command `close`.
A `close` without a number closes the current active plot window.

The gnuplot outboard driver, gnuplot_x11, is searched in a default place
chosen when the program is compiled.  You can override that by defining
the environment variable GNUPLOT_DRIVER_DIR to point to a different
location.

Plot windows will automatically be closed at the end of the session
unless the `-persist` option was given.

The options `persist` and @ref{raise} are unset by default, which means that
the defaults (persist == no and raise == yes) or the command line options
-persist / -raise or the Xresources are taken.  If [no]persist or
[no]raise are specified, they will override command line options and
Xresources.  Setting one of these options takes place immediately, so
the behaviour of an already running driver can be modified.  If the window
does not get raised, see discussion in @ref{raise}.

The option `title "<title name>"` will supply the title name of the window
for the current plot window or plot window <n> if a number is given.
Where (or if) this title is shown depends on your X window manager.

The size option can be used to set the size of the plot window.  The
size option will only apply to newly created windows.

The position option can be used to set the position of the plot window.  The
position option will only apply to newly created windows.

The size or aspect ratio of a plot may be changed by resizing the `gnuplot`
window.

Linewidths and pointsizes may be changed from within `gnuplot` with
`set linestyle`.

For terminal type `x11`, `gnuplot` accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file.  See the X(1) man page
(or its equivalent) for a description of such options.

@cindex X resources

A number of other `gnuplot` options are available for the `x11` terminal.
These may be specified either as command-line options when `gnuplot` is
invoked or as resources in the configuration file ".Xdefaults".  They are
set upon initialization and cannot be altered during a `gnuplot` session.
(except `persist` and @ref{raise})


@noindent --- X11_FONTS ---

@c ?commands set terminal x11 x11_fonts
@c ?set terminal x11 x11_fonts
@c ?set term x11 x11_fonts
@c ?x11 x11_fonts
@cindex x11_fonts

@cindex fonts

Upon initial startup, the default font is taken from the X11 resources
as set in the system or user .Xdefaults file or on the command line.

Example:
@example
      gnuplot*font: lucidasans-bold-12
@end example

A new default font may be specified to the x11 driver from inside
gnuplot using
@example
     `set term x11 font "<fontspec>"`
@end example

The driver first queries the X-server for a font of the exact name given.
If this query fails, then it tries to interpret <fontspec> as
"<font>,<size>,<slant>,<weight>" and to construct a full X11 font name
of the form
@example
      -*-<font>-<weight>-<s>-*-*-<size>-*-*-*-*-*-<encoding>

@end example

@example
 <font> is the base name of the font (e.g. Times or Symbol)
 <size> is the point size (defaults to 12 if not specified)
 <s> is `i` if <slant>=="italic" `o` if <slant>=="oblique" `r` otherwise
 <weight> is `medium` or `bold` if explicitly requested, otherwise `*`
 <encoding> is set based on the current character set (see @ref{encoding}).
@end example

So `set term x11 font "arial,15,italic"` will be translated to
-*-arial-*-i-*-*-15-*-*-*-*-*-iso8859-1 (assuming default encoding).
The <size>, <slant>, and <weight> specifications are all optional.
If you do not specify <slant> or <weight> then you will get whatever font 
variant the font server offers first.
You may set a default enconding via the corresponding X11 resource. E.g.
@example
      gnuplot*encoding: iso8859-15
@end example

The driver also recognizes some common PostScript font names and
replaces them with possible X11 or TrueType equivalents.
This same sequence is used to process font requests from @ref{label}.

If your gnuplot was built with configuration option --enable-x11-mbfonts,
you can specify multi-byte fonts by using the prefix "mbfont:" on the font
name. An additional font may be given, separated by a semicolon.
Since multi-byte font encodings are interpreted according to the locale
setting, you must make sure that the environmental variable LC_CTYPE is set
to some appropriate locale value such as ja_JP.eucJP, ko_KR.EUC, or zh_CN.EUC.

Example:
@example
      set term x11 font 'mbfont:kana14;k14'
            # 'kana14' and 'k14' are Japanese X11 font aliases, and ';'
            # is the separator of font names.
      set term x11 font 'mbfont:fixed,16,r,medium'
            # <font>,<size>,<slant>,<weight> form is also usable.
      set title '(mb strings)' font 'mbfont:*-fixed-medium-r-normal--14-*'

@end example

The same syntax applies to the default font in Xresources settings,
for example,
@example
      gnuplot*font: \\
          mbfont:-misc-fixed-medium-r-normal--14-*-*-*-c-*-jisx0208.1983-0

@end example

If gnuplot is built with --enable-x11-mbfonts, you can use two special
PostScript font names 'Ryumin-Light-*' and 'GothicBBB-Medium-*' (standard
Japanese PS fonts) without the prefix "mbfont:".



@noindent --- COMMAND-LINE_OPTIONS ---

@c ?commands set terminal x11 command-line-options
@c ?set terminal x11 command-line-options
@c ?set term x11 command-line-options
@c ?x11 command-line-options
@cindex command-line-options

In addition to the X Toolkit options, the following options may be specified
on the command line when starting `gnuplot` or as resources in your
".Xdefaults" file (note that @ref{raise} and `persist` can be overridden
later by `set term x11 [no]raise [no]persist)`:

@example
 `-mono`     forces monochrome rendering on color displays.
 `-gray`     requests grayscale rendering on grayscale or color displays.
             (Grayscale displays receive monochrome rendering by default.)
 `-clear`    requests that the window be cleared momentarily before a
             new plot is displayed.
 `-tvtwm`    requests that geometry specifications for position of the
             window be made relative to the currently displayed portion
             of the virtual root.
 `-raise`    raises plot window after each plot
 `-noraise`  does not raise plot window after each plot
 `-noevents` does not process mouse and key events
 `-ctrlq   ` closes window on ctrl-q rather than q
 `-persist`  plot windows survive after main gnuplot program exits

@end example

@cindex X resources

The options are shown above in their command-line syntax.  When entered as
resources in ".Xdefaults", they require a different syntax.

Example:
@example
      gnuplot*gray:  on
      gnuplot*ctrlq: on

@end example

`gnuplot` also provides a command line option (`-pointsize <v>`) and a
resource, `gnuplot*pointsize: <v>`, to control the size of points plotted
with the `points` plotting style.  The value `v` is a real number (greater
than 0 and less than or equal to ten) used as a scaling factor for point
sizes.  For example, `-pointsize 2` uses points twice the default size, and
`-pointsize 0.5` uses points half the normal size.

The `-noevents` switch disables all mouse and key event processing (except
for `q` and `<space>` for closing the window). This is useful for programs
which use the x11 driver independent of the gnuplot main program.

The `-ctrlq` switch changes the hot-key that closes a plot window from `q`
to `<ctrl>q`. This is useful is you are using the keystroke-capture feature
`pause mouse keystroke`, since it allows the character `q` to be captured
just as all other alphanumeric characters. The `-ctrlq` switch similarly
replaces the <space> hot-key with <ctrl><space> for the same reason.



@noindent --- MONOCHROME_OPTIONS ---

@c ?commands set terminal x11 monochrome_options
@c ?set terminal x11 monochrome_options
@c ?set term x11 monochrome_options
@c ?x11 monochrome_options
@cindex monochrome_options

@cindex X resources

For monochrome displays, `gnuplot` does not honor foreground or background
colors.  The default is black-on-white.  `-rv` or `gnuplot*reverseVideo: on`
requests white-on-black.



@noindent --- COLOR_RESOURCES ---

@c ?commands set terminal x11 color_resources
@c ?set terminal x11 color_resources
@c ?set term x11 color_resources
@c ?x11 color_resources
@cindex color_resources

@cindex X resources

For color displays, `gnuplot` honors the following resources (shown here
with their default values) or the greyscale resources.  The values may be
color names as listed in the X11 rgb.txt file on your system, hexadecimal
RGB color specifications (see X11 documentation), or a color name followed
by a comma and an `intensity` value from 0 to 1.  For example, `blue, 0.5`
means a half intensity blue.

@example
 gnuplot*background:  white
 gnuplot*textColor:   black
 gnuplot*borderColor: black
 gnuplot*axisColor:   black
 gnuplot*line1Color:  red
 gnuplot*line2Color:  green
 gnuplot*line3Color:  blue
 gnuplot*line4Color:  magenta
 gnuplot*line5Color:  cyan
 gnuplot*line6Color:  sienna
 gnuplot*line7Color:  orange
 gnuplot*line8Color:  coral

@end example


The command-line syntax for these is simple only for background,
which maps directly to the usual X11 toolkit option "-bg".  All
others can only be set on the command line by use of the generic
"-xrm" resource override option

Examples:

@example
      gnuplot -background coral
@end example

to change the background color.

@example
      gnuplot -xrm 'gnuplot*line1Color:blue'
@end example

to override the first linetype color.



@noindent --- GRAYSCALE_RESOURCES ---

@c ?commands set terminal x11 grayscale_resources
@c ?set terminal x11 grayscale_resources
@c ?set term x11 grayscale_resources
@c ?x11 grayscale_resources
@cindex grayscale_resources

@cindex X resources

When `-gray` is selected, `gnuplot` honors the following resources for
grayscale or color displays (shown here with their default values).  Note
that the default background is black.

@example
 gnuplot*background: black
 gnuplot*textGray:   white
 gnuplot*borderGray: gray50
 gnuplot*axisGray:   gray50
 gnuplot*line1Gray:  gray100
 gnuplot*line2Gray:  gray60
 gnuplot*line3Gray:  gray80
 gnuplot*line4Gray:  gray40
 gnuplot*line5Gray:  gray90
 gnuplot*line6Gray:  gray50
 gnuplot*line7Gray:  gray70
 gnuplot*line8Gray:  gray30

@end example




@noindent --- LINE_RESOURCES ---

@c ?commands set terminal x11 line_resources
@c ?set terminal x11 line_resources
@c ?set term x11 line_resources
@c ?x11 line_resources
@cindex line_resources

@cindex X resources

`gnuplot` honors the following resources for setting the width (in pixels) of
plot lines (shown here with their default values.)  0 or 1 means a minimal
width line of 1 pixel width.  A value of 2 or 3 may improve the appearance of
some plots.

@example
 gnuplot*borderWidth: 2
 gnuplot*axisWidth:   0
 gnuplot*line1Width:  0
 gnuplot*line2Width:  0
 gnuplot*line3Width:  0
 gnuplot*line4Width:  0
 gnuplot*line5Width:  0
 gnuplot*line6Width:  0
 gnuplot*line7Width:  0
 gnuplot*line8Width:  0

@end example


`gnuplot` honors the following resources for setting the dash style used for
plotting lines.  0 means a solid line.  A two-digit number `jk` (`j` and `k`
are >= 1 and <= 9) means a dashed line with a repeated pattern of `j` pixels
on followed by `k` pixels off.  For example, '16' is a dotted line with one
pixel on followed by six pixels off.  More elaborate on/off patterns can be
specified with a four-digit value.  For example, '4441' is four on, four off,
four on, one off.  The default values shown below are for monochrome displays
or monochrome rendering on color or grayscale displays.
Color displays default to dashed:off 

@example
 gnuplot*dashed:       off
 gnuplot*borderDashes:   0
 gnuplot*axisDashes:    16
 gnuplot*line1Dashes:    0
 gnuplot*line2Dashes:   42
 gnuplot*line3Dashes:   13
 gnuplot*line4Dashes:   44
 gnuplot*line5Dashes:   15
 gnuplot*line6Dashes: 4441
 gnuplot*line7Dashes:   42
 gnuplot*line8Dashes:   13

@end example

, "


@noindent --- X11 PM3D_RESOURCES ---

@c ?commands set terminal x11 pm3d_resources
@c ?set terminal x11 pm3d_resources
@c ?set term x11 pm3d_resources
@c ?x11 pm3d_resources
@cindex pm3d_resources

@c ?x11 pm3d
@cindex X resources

Choosing the appropriate visual class and number of colors is a crucial
point in X11 applications and a bit awkward, since X11 supports six visual
types in different depths.

By default `gnuplot` uses the default visual of the screen. The number of
colors which can be allocated depends on the visual class chosen. On a
visual class with a depth > 12bit, gnuplot starts with a maximal number
of 0x200 colors.  On a visual class with a depth > 8bit (but <= 12 bit)
the maximal number of colors is 0x100, on <= 8bit displays the maximum
number of colors is 240 (16 are left for line colors).

Gnuplot first starts to allocate the maximal number of colors as stated
above.  If this fails, the number of colors is reduced by the factor 2
until gnuplot gets all colors which are requested. If dividing `maxcolors`
by 2 repeatedly results in a number which is smaller than `mincolors`
`gnuplot` tries to install a private colormap. In this case the window
manager is responsible for swapping colormaps when the pointer is moved
in and out the x11 driver's window.

The default for `mincolors` is maxcolors / (num_colormaps > 1 ? 2 : 8),
where num_colormaps is the number of colormaps which are currently used
by gnuplot (usually 1, if only one x11 window is open).

Some systems support multiple (different) visual classes together on one
screen. On these systems it might be necessary to force gnuplot to use a
specific visual class, e.g. the default visual might be 8bit PseudoColor
but the screen would also support 24bit TrueColor which would be the
preferred choice.

The information about an Xserver's capabilities can be obtained with the
program `xdpyinfo`.  For the visual names below you can choose one of
StaticGray, GrayScale, StaticColor, PseudoColor, TrueColor, DirectColor.
If an Xserver supports a requested visual type at different depths,
`gnuplot` chooses the visual class with the highest depth (deepest).
If the requested visual class matches the default visual and multiple
classes of this type are supported, the default visual is preferred.

Example: on an 8bit PseudoColor visual you can force a private color map
by specifying `gnuplot*maxcolors: 240` and `gnuplot*mincolors: 240`.


@example
 gnuplot*maxcolors:  <integer>
 gnuplot*mincolors:  <integer>
 gnuplot*visual:     <visual name>

@end example

, "


@noindent --- X11 OTHER_RESOURCES ---

@c ?commands set terminal x11 other_resources
@c ?set terminal x11 other_resources
@c ?set term x11 other_resources
@c ?x11 other_resources
@cindex X resources

By default the contents of the current plot window are exported to the X11
clipboard in response to X events in the window. Setting the resource
'gnuplot*exportselection' to 'off' or 'false' will disable this.

By default text rotation is done using a method that is fast, but can
corrupt nearby colors depending on the background.  If this is a problem,
you can set the resource 'gnuplot.fastrotate' to 'off'


@example
 gnuplot*exportselection:  off
 gnuplot*fastrotate:  on
 gnuplot*ctrlq:  off

@end example



@node x11_, xlib, x11, terminal_
@subsubsection x11

@c ?commands set terminal x11
@c ?set terminal x11
@c ?set term x11
@c ?terminal x11
@c ?term x11
@cindex x11

@cindex X11

`gnuplot` provides the `x11` terminal type for use with X servers.  This
terminal type is set automatically at startup if the `DISPLAY` environment
variable is set, if the `TERM` environment variable is set to `xterm`, or
if the `-display` command line option is used.

Syntax:
@example
   set terminal x11 @{<n>@}
                    @{title "<string>"@}
                    @{@{no@}enhanced@} @{font <fontspec>@}
                    @{linewidth LW@} @{solid|dashed@}
                    @{@{no@}persist@} @{@{no@}raise@} @{@{no@}ctrlq@}
                    @{close@}
                    @{size XX,YY@} @{position XX,YY@}
   set terminal x11 @{reset@}

@end example

Multiple plot windows are supported: `set terminal x11 <n>` directs the
output to plot window number n.  If n is not 0, the terminal number will be
appended to the window title (unless a title has been supplied manually)
and the icon will be labeled `Gnuplot <n>`.  The active window may be
distinguished by a change in cursor (from default to crosshair).

The x11 terminal support enhanced text mode (see `enhanced`), subject
to the available fonts. In order for font size commands embedded in text
to have any effect, the default x11 font must be scalable. Thus the first
example below will work as expected, but the second will not.

@example
   set term x11 enhanced font "arial,15" 
   set title '@{/=20 Big@} Medium @{/=5 Small@}' 

@end example

@example
   set term x11 enhanced font "terminal-14" 
   set title '@{/=20 Big@} Medium @{/=5 Small@}' 

@end example

Plot windows remain open even when the `gnuplot` driver is changed to a
different device.  A plot window can be closed by pressing the letter q
while that window has input focus, or by choosing `close` from a window
manager menu.  All plot windows can be closed by specifying @ref{reset}, which
actually terminates the subprocess which maintains the windows (unless
`-persist` was specified).  The `close` command can be used to close
individual plot windows by number.  However, after a @ref{reset}, those plot
windows left due to persist cannot be closed with the command `close`.
A `close` without a number closes the current active plot window.

The gnuplot outboard driver, gnuplot_x11, is searched in a default place
chosen when the program is compiled.  You can override that by defining
the environment variable GNUPLOT_DRIVER_DIR to point to a different
location.

Plot windows will automatically be closed at the end of the session
unless the `-persist` option was given.

The options `persist` and @ref{raise} are unset by default, which means that
the defaults (persist == no and raise == yes) or the command line options
-persist / -raise or the Xresources are taken.  If [no]persist or
[no]raise are specified, they will override command line options and
Xresources.  Setting one of these options takes place immediately, so
the behaviour of an already running driver can be modified.  If the window
does not get raised, see discussion in @ref{raise}.

The option `title "<title name>"` will supply the title name of the window
for the current plot window or plot window <n> if a number is given.
Where (or if) this title is shown depends on your X window manager.

The size option can be used to set the size of the plot window.  The
size option will only apply to newly created windows.

The position option can be used to set the position of the plot window.  The
position option will only apply to newly created windows.

The size or aspect ratio of a plot may be changed by resizing the `gnuplot`
window.

Linewidths and pointsizes may be changed from within `gnuplot` with
`set linestyle`.

For terminal type `x11`, `gnuplot` accepts (when initialized) the standard
X Toolkit options and resources such as geometry, font, and name from the
command line arguments or a configuration file.  See the X(1) man page
(or its equivalent) for a description of such options.

@cindex X resources

A number of other `gnuplot` options are available for the `x11` terminal.
These may be specified either as command-line options when `gnuplot` is
invoked or as resources in the configuration file ".Xdefaults".  They are
set upon initialization and cannot be altered during a `gnuplot` session.
(except `persist` and @ref{raise})


@noindent --- X11_FONTS ---

@c ?commands set terminal x11 x11_fonts
@c ?set terminal x11 x11_fonts
@c ?set term x11 x11_fonts
@c ?x11 x11_fonts
@cindex x11_fonts

@cindex fonts

Upon initial startup, the default font is taken from the X11 resources
as set in the system or user .Xdefaults file or on the command line.

Example:
@example
      gnuplot*font: lucidasans-bold-12
@end example

A new default font may be specified to the x11 driver from inside
gnuplot using
@example
     `set term x11 font "<fontspec>"`
@end example

The driver first queries the X-server for a font of the exact name given.
If this query fails, then it tries to interpret <fontspec> as
"<font>,<size>,<slant>,<weight>" and to construct a full X11 font name
of the form
@example
      -*-<font>-<weight>-<s>-*-*-<size>-*-*-*-*-*-<encoding>

@end example

@example
 <font> is the base name of the font (e.g. Times or Symbol)
 <size> is the point size (defaults to 12 if not specified)
 <s> is `i` if <slant>=="italic" `o` if <slant>=="oblique" `r` otherwise
 <weight> is `medium` or `bold` if explicitly requested, otherwise `*`
 <encoding> is set based on the current character set (see @ref{encoding}).
@end example

So `set term x11 font "arial,15,italic"` will be translated to
-*-arial-*-i-*-*-15-*-*-*-*-*-iso8859-1 (assuming default encoding).
The <size>, <slant>, and <weight> specifications are all optional.
If you do not specify <slant> or <weight> then you will get whatever font 
variant the font server offers first.
You may set a default enconding via the corresponding X11 resource. E.g.
@example
      gnuplot*encoding: iso8859-15
@end example

The driver also recognizes some common PostScript font names and
replaces them with possible X11 or TrueType equivalents.
This same sequence is used to process font requests from @ref{label}.

If your gnuplot was built with configuration option --enable-x11-mbfonts,
you can specify multi-byte fonts by using the prefix "mbfont:" on the font
name. An additional font may be given, separated by a semicolon.
Since multi-byte font encodings are interpreted according to the locale
setting, you must make sure that the environmental variable LC_CTYPE is set
to some appropriate locale value such as ja_JP.eucJP, ko_KR.EUC, or zh_CN.EUC.

Example:
@example
      set term x11 font 'mbfont:kana14;k14'
            # 'kana14' and 'k14' are Japanese X11 font aliases, and ';'
            # is the separator of font names.
      set term x11 font 'mbfont:fixed,16,r,medium'
            # <font>,<size>,<slant>,<weight> form is also usable.
      set title '(mb strings)' font 'mbfont:*-fixed-medium-r-normal--14-*'

@end example

The same syntax applies to the default font in Xresources settings,
for example,
@example
      gnuplot*font: \\
          mbfont:-misc-fixed-medium-r-normal--14-*-*-*-c-*-jisx0208.1983-0

@end example

If gnuplot is built with --enable-x11-mbfonts, you can use two special
PostScript font names 'Ryumin-Light-*' and 'GothicBBB-Medium-*' (standard
Japanese PS fonts) without the prefix "mbfont:".



@noindent --- COMMAND-LINE_OPTIONS ---

@c ?commands set terminal x11 command-line-options
@c ?set terminal x11 command-line-options
@c ?set term x11 command-line-options
@c ?x11 command-line-options
@cindex command-line-options

In addition to the X Toolkit options, the following options may be specified
on the command line when starting `gnuplot` or as resources in your
".Xdefaults" file (note that @ref{raise} and `persist` can be overridden
later by `set term x11 [no]raise [no]persist)`:

@example
 `-mono`     forces monochrome rendering on color displays.
 `-gray`     requests grayscale rendering on grayscale or color displays.
             (Grayscale displays receive monochrome rendering by default.)
 `-clear`    requests that the window be cleared momentarily before a
             new plot is displayed.
 `-tvtwm`    requests that geometry specifications for position of the
             window be made relative to the currently displayed portion
             of the virtual root.
 `-raise`    raises plot window after each plot
 `-noraise`  does not raise plot window after each plot
 `-noevents` does not process mouse and key events
 `-ctrlq   ` closes window on ctrl-q rather than q
 `-persist`  plot windows survive after main gnuplot program exits

@end example

@cindex X resources

The options are shown above in their command-line syntax.  When entered as
resources in ".Xdefaults", they require a different syntax.

Example:
@example
      gnuplot*gray:  on
      gnuplot*ctrlq: on

@end example

`gnuplot` also provides a command line option (`-pointsize <v>`) and a
resource, `gnuplot*pointsize: <v>`, to control the size of points plotted
with the `points` plotting style.  The value `v` is a real number (greater
than 0 and less than or equal to ten) used as a scaling factor for point
sizes.  For example, `-pointsize 2` uses points twice the default size, and
`-pointsize 0.5` uses points half the normal size.

The `-noevents` switch disables all mouse and key event processing (except
for `q` and `<space>` for closing the window). This is useful for programs
which use the x11 driver independent of the gnuplot main program.

The `-ctrlq` switch changes the hot-key that closes a plot window from `q`
to `<ctrl>q`. This is useful is you are using the keystroke-capture feature
`pause mouse keystroke`, since it allows the character `q` to be captured
just as all other alphanumeric characters. The `-ctrlq` switch similarly
replaces the <space> hot-key with <ctrl><space> for the same reason.



@noindent --- MONOCHROME_OPTIONS ---

@c ?commands set terminal x11 monochrome_options
@c ?set terminal x11 monochrome_options
@c ?set term x11 monochrome_options
@c ?x11 monochrome_options
@cindex monochrome_options

@cindex X resources

For monochrome displays, `gnuplot` does not honor foreground or background
colors.  The default is black-on-white.  `-rv` or `gnuplot*reverseVideo: on`
requests white-on-black.



@noindent --- COLOR_RESOURCES ---

@c ?commands set terminal x11 color_resources
@c ?set terminal x11 color_resources
@c ?set term x11 color_resources
@c ?x11 color_resources
@cindex color_resources

@cindex X resources

For color displays, `gnuplot` honors the following resources (shown here
with their default values) or the greyscale resources.  The values may be
color names as listed in the X11 rgb.txt file on your system, hexadecimal
RGB color specifications (see X11 documentation), or a color name followed
by a comma and an `intensity` value from 0 to 1.  For example, `blue, 0.5`
means a half intensity blue.

@example
 gnuplot*background:  white
 gnuplot*textColor:   black
 gnuplot*borderColor: black
 gnuplot*axisColor:   black
 gnuplot*line1Color:  red
 gnuplot*line2Color:  green
 gnuplot*line3Color:  blue
 gnuplot*line4Color:  magenta
 gnuplot*line5Color:  cyan
 gnuplot*line6Color:  sienna
 gnuplot*line7Color:  orange
 gnuplot*line8Color:  coral

@end example


The command-line syntax for these is simple only for background,
which maps directly to the usual X11 toolkit option "-bg".  All
others can only be set on the command line by use of the generic
"-xrm" resource override option

Examples:

@example
      gnuplot -background coral
@end example

to change the background color.

@example
      gnuplot -xrm 'gnuplot*line1Color:blue'
@end example

to override the first linetype color.



@noindent --- GRAYSCALE_RESOURCES ---

@c ?commands set terminal x11 grayscale_resources
@c ?set terminal x11 grayscale_resources
@c ?set term x11 grayscale_resources
@c ?x11 grayscale_resources
@cindex grayscale_resources

@cindex X resources

When `-gray` is selected, `gnuplot` honors the following resources for
grayscale or color displays (shown here with their default values).  Note
that the default background is black.

@example
 gnuplot*background: black
 gnuplot*textGray:   white
 gnuplot*borderGray: gray50
 gnuplot*axisGray:   gray50
 gnuplot*line1Gray:  gray100
 gnuplot*line2Gray:  gray60
 gnuplot*line3Gray:  gray80
 gnuplot*line4Gray:  gray40
 gnuplot*line5Gray:  gray90
 gnuplot*line6Gray:  gray50
 gnuplot*line7Gray:  gray70
 gnuplot*line8Gray:  gray30

@end example




@noindent --- LINE_RESOURCES ---

@c ?commands set terminal x11 line_resources
@c ?set terminal x11 line_resources
@c ?set term x11 line_resources
@c ?x11 line_resources
@cindex line_resources

@cindex X resources

`gnuplot` honors the following resources for setting the width (in pixels) of
plot lines (shown here with their default values.)  0 or 1 means a minimal
width line of 1 pixel width.  A value of 2 or 3 may improve the appearance of
some plots.

@example
 gnuplot*borderWidth: 2
 gnuplot*axisWidth:   0
 gnuplot*line1Width:  0
 gnuplot*line2Width:  0
 gnuplot*line3Width:  0
 gnuplot*line4Width:  0
 gnuplot*line5Width:  0
 gnuplot*line6Width:  0
 gnuplot*line7Width:  0
 gnuplot*line8Width:  0

@end example


`gnuplot` honors the following resources for setting the dash style used for
plotting lines.  0 means a solid line.  A two-digit number `jk` (`j` and `k`
are >= 1 and <= 9) means a dashed line with a repeated pattern of `j` pixels
on followed by `k` pixels off.  For example, '16' is a dotted line with one
pixel on followed by six pixels off.  More elaborate on/off patterns can be
specified with a four-digit value.  For example, '4441' is four on, four off,
four on, one off.  The default values shown below are for monochrome displays
or monochrome rendering on color or grayscale displays.
Color displays default to dashed:off 

@example
 gnuplot*dashed:       off
 gnuplot*borderDashes:   0
 gnuplot*axisDashes:    16
 gnuplot*line1Dashes:    0
 gnuplot*line2Dashes:   42
 gnuplot*line3Dashes:   13
 gnuplot*line4Dashes:   44
 gnuplot*line5Dashes:   15
 gnuplot*line6Dashes: 4441
 gnuplot*line7Dashes:   42
 gnuplot*line8Dashes:   13

@end example

, "


@noindent --- X11 PM3D_RESOURCES ---

@c ?commands set terminal x11 pm3d_resources
@c ?set terminal x11 pm3d_resources
@c ?set term x11 pm3d_resources
@c ?x11 pm3d_resources
@cindex pm3d_resources

@c ?x11 pm3d
@cindex X resources

Choosing the appropriate visual class and number of colors is a crucial
point in X11 applications and a bit awkward, since X11 supports six visual
types in different depths.

By default `gnuplot` uses the default visual of the screen. The number of
colors which can be allocated depends on the visual class chosen. On a
visual class with a depth > 12bit, gnuplot starts with a maximal number
of 0x200 colors.  On a visual class with a depth > 8bit (but <= 12 bit)
the maximal number of colors is 0x100, on <= 8bit displays the maximum
number of colors is 240 (16 are left for line colors).

Gnuplot first starts to allocate the maximal number of colors as stated
above.  If this fails, the number of colors is reduced by the factor 2
until gnuplot gets all colors which are requested. If dividing `maxcolors`
by 2 repeatedly results in a number which is smaller than `mincolors`
`gnuplot` tries to install a private colormap. In this case the window
manager is responsible for swapping colormaps when the pointer is moved
in and out the x11 driver's window.

The default for `mincolors` is maxcolors / (num_colormaps > 1 ? 2 : 8),
where num_colormaps is the number of colormaps which are currently used
by gnuplot (usually 1, if only one x11 window is open).

Some systems support multiple (different) visual classes together on one
screen. On these systems it might be necessary to force gnuplot to use a
specific visual class, e.g. the default visual might be 8bit PseudoColor
but the screen would also support 24bit TrueColor which would be the
preferred choice.

The information about an Xserver's capabilities can be obtained with the
program `xdpyinfo`.  For the visual names below you can choose one of
StaticGray, GrayScale, StaticColor, PseudoColor, TrueColor, DirectColor.
If an Xserver supports a requested visual type at different depths,
`gnuplot` chooses the visual class with the highest depth (deepest).
If the requested visual class matches the default visual and multiple
classes of this type are supported, the default visual is preferred.

Example: on an 8bit PseudoColor visual you can force a private color map
by specifying `gnuplot*maxcolors: 240` and `gnuplot*mincolors: 240`.


@example
 gnuplot*maxcolors:  <integer>
 gnuplot*mincolors:  <integer>
 gnuplot*visual:     <visual name>

@end example

, "


@noindent --- X11 OTHER_RESOURCES ---

@c ?commands set terminal x11 other_resources
@c ?set terminal x11 other_resources
@c ?set term x11 other_resources
@c ?x11 other_resources
@cindex X resources

By default the contents of the current plot window are exported to the X11
clipboard in response to X events in the window. Setting the resource
'gnuplot*exportselection' to 'off' or 'false' will disable this.

By default text rotation is done using a method that is fast, but can
corrupt nearby colors depending on the background.  If this is a problem,
you can set the resource 'gnuplot.fastrotate' to 'off'


@example
 gnuplot*exportselection:  off
 gnuplot*fastrotate:  on
 gnuplot*ctrlq:  off

@end example



@node xlib, xlib_, x11_, terminal_
@subsubsection xlib

@c ?commands set terminal xlib
@c ?set terminal xlib
@c ?set term xlib
@c ?terminal xlib
@c ?term xlib
@cindex xlib
@tmindex xlib


The `xlib` terminal driver supports the X11 Windows System.  It generates
gnuplot_x11 commands, but sends them to the output file specified by
`set output '<filename>'`. `set term x11` is equivalent to
`set output "|gnuplot_x11 -noevents"; set term xlib.`
`xlib` takes the same set of options as `x11`."

@node xlib_,  , xlib, terminal_
@subsubsection xlib

@c ?commands set terminal xlib
@c ?set terminal xlib
@c ?set term xlib
@c ?terminal xlib
@c ?term xlib
@cindex xlib
@tmindex xlib


The `xlib` terminal driver supports the X11 Windows System.  It generates
gnuplot_x11 commands, but sends them to the output file specified by
`set output '<filename>'`. `set term x11` is equivalent to
`set output "|gnuplot_x11 -noevents"; set term xlib.`
`xlib` takes the same set of options as `x11`."

@node Graphical_User_Interfaces, Bugs, Terminal_types, Top
@chapter Graphical User Interfaces

@c ?graphical user interfaces
@cindex gui's

Several graphical user interfaces have been written for `gnuplot` and one for
win32 is included in this distribution.  In addition, there is a Python
interface at
@uref{http://py-gnuplot.darwinports.com/,http://py-gnuplot.darwinports.com/
}

Also several X11 interfaces exist.
One of them is called xgfe. It uses the Qt library and can be found on
@uref{http://www.flash.net/~dmishee/xgfe/xgfe.html,http://www.flash.net/~dmishee/xgfe/xgfe.html
}

In addition three Tcl/Tk located at the usual Tcl/Tk repositories exist.

Bruce Ravel (ravel@@phys.washington.edu) has written a new version of
gnuplot-mode for GNU emacs and XEmacs. This version is based on
the gnuplot.el file by Gershon Elber.
While the gnuplot CVS repository has its own copy the most recent
version of this package is available from
@uref{http://feff.phys.washington.edu/~ravel/software/gnuplot-mode/,http://feff.phys.washington.edu/~ravel/software/gnuplot-mode/
}


@menu
* Bugs::                        
@end menu

@node Bugs, Concept_Index, Graphical_User_Interfaces, Top
@chapter Bugs

@cindex bugs

Bugs reported since the current release as well as older ones
may be located via the official distribution site on SourceForge.

Please e-mail bug reports to the gnuplot-bugs mailing list.
Or upload the report to the gnuplot web site on SourceForge.
Please give complete information on the version of gnuplot you are using
and, if possible, a test script that demonstrates the bug.
See @ref{Seeking-assistance}.

The sections below list problems known to be present in gnuplot version 4.2 at
the time of release.  Some of these are actually bugs in external support
libraries and may have been fixed indepently of any changes in gnuplot.


@menu
* Gnuplot_limitations::         
* External_libraries::          
@end menu

@node Gnuplot_limitations, External_libraries, Bugs, Bugs
@section Gnuplot limitations

@c ?bugs gnuplot
@cindex gamma
@findex gamma


@cindex bessel

@cindex timefmt
@opindex timefmt


@cindex load
@cmindex load


@cindex nohidden3d

Floating point exceptions (floating point number too large/small, divide by
zero, etc.) may occasionally be generated by user defined functions.  Some of
the demos in particular may cause numbers to exceed the floating point range.
Whether the system ignores such exceptions (in which case `gnuplot` labels
the corresponding point as undefined) or aborts `gnuplot` depends on the
compiler/runtime environment.

The gamma and bessel functions do not work for complex arguments.

If a command line contains a "load" command, then anything on the line after
the "load <filename>" is ignored.

Only one color palette at a time is active for any given x11 plot window.
This means that multiplots whose constituent plots use different palettes
will not display correctly in x11.

Coordinates specified as "time" wrap at 24 hours, and have a precision limited
to 1 second.  This is in particular a limitation in using time format to
handle geographic coordinates.

Error bars are not handled properly in polar/spherical coordinate plot modes.

The 'nohidden3d' option that is supposed to exempt individual plots from the
global property 'set hidden3d' does not work for parametric curves.


@node External_libraries,  , Gnuplot_limitations, Bugs
@section External libraries

@c ?bugs external_libraries
@cindex libgd

@cindex svgalib
@tmindex svgalib


@cindex locale
@opindex locale


@cindex internationalization

@cindex pdf
@tmindex pdf


External library GD (used by PNG/JPEG/GIF drivers):
Versions of libgd through 2.0.33 contain various bugs in mapping the characters
of Adobe's Symbol font.  Also it is possible to trigger a library segfault if
an anti-aliased line crosses an upper corner of the canvas.

External library PDFlib (used by PDF driver):
Gnuplot can be linked against libpdf versions 4, 5, or 6. However, these
versions differ in their handling of piped I/O.  Therefore gnuplot scripts
using piped output to PDF may work only for some versions of PDFlib.

External library svgalib (used by linux and vgagl driver):
Requires gnuplot to be suid root (bad!) and has many bugs that are specific
to the video card or graphics driver used in X11.

Internationalization (locale settings):
Gnuplot uses the C runtime library routine setlocale() to control
locale-specific formatting of input and output number, times, and date strings.
The locales available, and the level of support for locale features such as
"thousands' grouping separator", depend on the internationalization support
provided by your individual machine.
@node Concept_Index, Command_Index, Bugs, Top
@unnumbered Concept Index
@printindex cp

@node Command_Index, Options_Index, Concept_Index, Top
@unnumbered Command Index
@printindex cm

@node Options_Index, Function_Index, Command_Index, Top
@unnumbered Options Index
@printindex op

@node Function_Index, Terminal_Index, Options_Index, Top
@unnumbered Function Index
@printindex fn

@node Terminal_Index,  , Function_Index, Top
@unnumbered Terminal Index
@printindex tm

@c @shortcontents
@contents
@bye