The GNU plotting utilities consist of eight command-line programs: the
graphics programs graph, plot, pic2plot,
tek2plot, and plotfont, and the mathematical programs
spline, ode, and double. Distributed with these
programs is GNU libplot, the library on which the graphics
programs are based. GNU libplot is a function library for
device-independent two-dimensional vector graphics, including vector
graphics animations under the X Window System. It has bindings
for both C and C++.
The graphics programs and GNU libplot can export vector graphics
in the following formats.
display, which is part of the free ImageMagick
package.
netpbm package, or viewed
with display.
display.
idraw-editable Postscript format. Files in this format
may be sent to a Postscript printer, imported into another document, or
edited with the free idraw drawing editor. See idraw.
xfig drawing editor. See xfig.
dxterm.
xterm terminal
emulator program and the MS-DOS version of kermit.
plot program can translate it to any of the preceding formats.
Of the command-line graphics programs, the best known is graph,
which is an application for plotting two-dimensional scientific data.
It reads one or more data files containing datasets, and outputs a plot.
The above output formats are supported. The corresponding commands are
graph -T X, graph -T png, graph -T pnm,
graph -T gif, graph -T svg, graph -T ai,
graph -T ps, graph -T cgm, graph -T fig,
graph -T pcl, graph -T hpgl, graph -T regis,
graph -T tek, and graph. graph without a ‘-T’
option (referred to as `raw graph') produces output in GNU
metafile format.
graph can read datasets in both ASCII and binary format, and
datasets in the `table' format produced by the plotting program
gnuplot. It produces a plot with or without axes and labels.
You may specify labels and ranges for the axes, and the size and
position of the plot on the display. The labels may contain subscripts
and subscripts, Greek letters, and other special symbols; there is also
support for Cyrillic script (i.e., Russian) and Japanese. You may
specify the type of marker symbol used for each dataset, and such
parameters as the style and thickness of the line (if any) used to
connect points in a dataset. The plotting of filled regions is
supported, as is the drawing of error bars. graph provides full
support for multiplotting. With a single invocation of graph,
you may produce a multiplot consisting of many plots, either side by
side or inset. Each plot will have its own axes and data.
graph -T X, graph -T tek, graph -T regis, and
raw graph have a feature that most plotting programs do not have.
They can accept input from a pipe, and plot data points to the output in
real time. For this to occur, the user must specify ranges for both
axes, so that graph does not need to wait until the end of the
input before determining them.
The plot program is a so-called plot filter. It can translate
GNU graphics metafiles (produced for example by raw graph)
into any supported output format. The corresponding commands are
plot -T X, plot -T png, plot -T pnm, plot
-T gif, plot -T svg, plot -T ai, plot -T ps,
plot -T cgm, plot -T fig, plot -T pcl, plot
-T hpgl, plot -T regis, plot -T tek, and plot.
The plot program is useful if you wish to produce output in
several different formats while invoking graph only once. It is also useful if you wish to translate files in the traditional
`plot(5)' format produced by, e.g., the non-GNU versions of graph
provided with some operating systems. GNU metafile format is compatible
with plot(5) format.
The pic2plot program can translate from the pic language to any
supported output format. The pic language, which was invented at Bell
Laboratories, is used for creating box-and-arrow diagrams of the kind
frequently found in technical papers and textbooks. The corresponding
commands are pic2plot -T X, pic2plot -T png,
pic2plot -T pnm, pic2plot -T gif, pic2plot -T ai,
pic2plot -T ps, pic2plot -T cgm, pic2plot -T fig,
pic2plot -T pcl, pic2plot -T hpgl, pic2plot -T
regis, pic2plot -T tek, and pic2plot.
The tek2plot program can translate from Tektronix format to any
supported output format. The corresponding commands are tek2plot
-T X, tek2plot -T png, tek2plot -T pnm,
tek2plot -T gif, tek2plot -T svg, tek2plot -T ai,
tek2plot -T ps, tek2plot -T cgm, tek2plot -T fig,
tek2plot -T pcl, tek2plot -T hpgl, tek2plot -T
regis, and tek2plot. tek2plot is useful if you have an
older application that produces drawings in Tektronix format.
The plotfont program is a simple utility that displays a
character map for any font that is available to graph,
plot, pic2plot, or tek2plot. The 35 standard
Postscript fonts are available if the ‘-T X’, ‘-T ai’,
‘-T ps’, ‘-T cgm’, or ‘-T fig’ options are used. The 45
standard PCL 5 fonts (i.e., “LaserJet” fonts) are available if the
‘-T ai’, ‘-T pcl’ or ‘-T hpgl’ options are used. In the
latter two cases (‘-T pcl’ and ‘-T hpgl’), a number of
Hewlett–Packard vector fonts are available as well. A set of
22 Hershey vector fonts, including Cyrillic fonts and a Japanese font,
is always available. When producing output for an X Window System
display, any of the graphics programs can use scalable X fonts.
Of the command-line mathematical programs, spline does spline
interpolation of scalar or vector-valued data. It normally uses either
cubic spline interpolation or exponential splines in tension, but like
graph it can function as a real-time filter under some
circumstances. Besides splining datasets, it can construct curves,
either open or closed, through arbitrarily chosen points in
d-dimensional space. ode provides the ability to
integrate an ordinary differential equation or a system of ordinary
differential equations, when provided with an explicit expression for
each equation. It supplements the plotting program gnuplot,
which can plot functions but not integrate ordinary differential
equations. The final command-line mathematical program, double,
is a filter for converting, scaling and cutting binary or ASCII data
streams. It is still under development and is not yet documented.
The GNU libplot function library, on which the command-line
graphics programs are based, is discussed at length elsewhere in
this documentation. It gives C and C++ programs the ability to
draw such objects as lines, open and closed polylines, arcs (both
circular and elliptic), quadratic and cubic Bezier curves, circles and
ellipses, points (i.e., pixels), marker symbols, and text strings. The
filling of objects other than points, marker symbols, and text strings
is supported (fill color, as well as pen color, can be set
arbitrarily). Text strings can be drawn in any of a large number of
fonts. The 35 standard Postscript fonts are supported by the X Window System, SVG, Illustrator, Postscript, CGM, and xfig
drivers, and the 45 standard PCL 5 fonts are supported by the SVG,
Illustrator, PCL 5 and HP-GL/2 drivers. The latter two also support
a number of Hewlett–Packard vector fonts. All drivers, including the
PNG, PNM, GIF, ReGIS, Tektronix and metafile drivers, support a set of
22 Hershey vector fonts.
The support for drawing text strings is extensive. Text strings may
include subscripts and superscripts, and may include characters chosen
from more than one font in a typeface. Many non-alphanumeric characters
may be included. The entire collection of over 1700 `Hershey glyphs'
digitized by Allen V. Hershey at the U.S. Naval Surface Weapons
Center, which includes many curious symbols, is built into GNU
libplot. Text strings in the so-called EUC-JP encoding (the
Extended Unix Code for Japanese) can be also be drawn. Such strings may
include both syllabic Japanese characters (Hiragana and Katakana) and
ideographic Japanese characters (Kanji). GNU libplot contains a
library of 603 Kanji, including 596 of the 2965 frequently used
Level 1 Kanji.