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Introduction

Gnuplot is a command-line driven graphing utility that is copyrighted but freely distributed. Designed for efficient and interactive visualization of mathematical functions and data. It has the capacity for generating publication quality figures of 2 or 3 dimensions composed of lines, points, boxes, contours, vector fields, surfaces and texts.

Versions

Gnuplot is installed on most Compute Canada/SHARCNET systems as part of the default software stack.

To see the latest versions available, run:

module avail gnuplot

and then load the desired modules.

Example plots

Set up

The following examples can be run Compute Canada systems.

  • Login to the system enabling X11 forwarding with the -Y option to ssh:
   $ ssh -Y your_username_here@graham.computecanada.ca

  • Then launch the program:
$ gnuplot
 
	G N U P L O T
	Version 5.0 patchlevel 3    last modified 2016-02-21
 
	Copyright (C) 1986-1993, 1998, 2004, 2007-2016
	Thomas Williams, Colin Kelley and many others
 
	gnuplot home:     http://www.gnuplot.info
	faq, bugs, etc:   type "help FAQ"
	immediate help:   type "help"  (plot window: hit 'h')
 
Terminal type set to 'x11'
gnuplot>


Once that "gnuplot>" prompt is in the terminal (that is set to 'X11') the following examples can be pasted to generate the example figures.

Example 1: multiple axis scaling

Put the code below into a file called example1.in

# Use the 3rd plot of the electronics demo to show off
# the use of multiple x and y axes in the same plot.
# 
A(jw) = ({0,1}*jw/({0,1}*jw+p1)) * (1/(1+{0,1}*jw/p2))
p1 = 10
p2 = 10000
set dummy jw
set grid x y2
set key center top title " "
set logscale xy
set log x2
unset log y2
set title "Transistor Amplitude and Phase Frequency Response"
set xlabel "jw (radians)"
set xrange [1.1 : 90000.0]
set x2range [1.1 : 90000.0]
set ylabel "magnitude of A(jw)"
set y2label "Phase of A(jw) (degrees)"
set ytics nomirror
set y2tics
set tics out
set autoscale  y
set autoscale y2
plot abs(A(jw)) axes x1y1, 180./pi*arg(A(jw)) axes x2y2

Call the script in gnuplot to generate the figure as follows:

figure resulting from demo commands
Figure produced on orc-dev# with commands from "multiple axis scales" at [gnuplot examples]
gnuplot> call "example1.in"
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Example 2: 3D surface

Put the code below into a file called example2.in

set samples 21
set isosample 11
set xlabel "X axis" offset -3,-2
set ylabel "Y axis" offset 3,-2
set zlabel "Z axis" offset -5
set title "3D gnuplot demo"
set label 1 "This is the surface boundary" at -10,-5,150 center
set arrow 1 from -10,-5,120 to -10,0,0 nohead
set arrow 2 from -10,-5,120 to 10,0,0 nohead
set arrow 3 from -10,-5,120 to 0,10,0 nohead
set arrow 4 from -10,-5,120 to 0,-10,0 nohead
set xrange [-10:10]
set yrange [-10:10]
splot x*y

Call the script in gnuplot to generate the figure as follows:

figure resulting from demo commands
Figure produced on orc-dev# with commands from "surfaces 1" at [gnuplot examples]
gnuplot> call "example2.in"
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Example 3: 3D hidden surfaces

Put the code below into a file called example3.in

# Another example of pm3d hidden surface removal,
# this time using pm3d depth-ordering
#
set multiplot title "Interlocking Tori"
set title "PM3D surface\nno depth sorting"

set parametric
set urange [-pi:pi]
set vrange [-pi:pi]
set isosamples 50,20

set origin -0.02,0.0
set size 0.55, 0.9

unset key
unset xtics
unset ytics
unset ztics
set border 0
set view 60, 30, 1.5, 0.9
unset colorbox

set pm3d scansbackward
splot cos(u)+.5*cos(u)*cos(v),sin(u)+.5*sin(u)*cos(v),.5*sin(v) with pm3d, \
      1+cos(u)+.5*cos(u)*cos(v),.5*sin(v),sin(u)+.5*sin(u)*cos(v) with pm3d

set title "PM3D surface\ndepth sorting"

set origin 0.40,0.0
set size 0.55, 0.9
set colorbox vertical user origin 0.9, 0.15 size 0.02, 0.50
set format cb "%.1f"

set pm3d depthorder
splot cos(u)+.5*cos(u)*cos(v),sin(u)+.5*sin(u)*cos(v),.5*sin(v) with pm3d, \
      1+cos(u)+.5*cos(u)*cos(v),.5*sin(v),sin(u)+.5*sin(u)*cos(v) with pm3d

unset multiplot

Call the script in gnuplot to generate the figure as follows:

figure resulting from demo commands
Figure produced on orc-dev# with commands from "pm3d hidden surfaces" at [gnuplot examples]
gnuplot> call "example3.in"
 
 
 
 
 
 
 
 
 
 
 
 
 
 

References

o Online Documentation
http://www.gnuplot.info/documentation.html

o A brief gnuplot tutorial by Henri Gavin
http://people.duke.edu/~hpgavin/gnuplot.html

o Demo Scripts for gnuplot version 5
http://www.gnuplot.info/demo/