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6. Graphics

Among the scores of graphic packages available, gnuplot stands out for its power and ease of use. Go to X and type gnuplot, and have two sample data files ready: 2D-data.dat (two data per line), and 3D-data.dat (three data per line).

Examples of 2-D graphs:

gnuplot> set title "my first graph"
gnuplot> plot '2D-data.dat'
gnuplot> plot '2D-data.dat' with linespoints
gnuplot> plot '2D-data.dat', sin(x)
gnuplot> plot [-5:10] '2D-data.dat'

Example of 3-D graphs (each `row' of X values is followed by a blank line):

gnuplot> set parametric ; set hidden3d ; set contour
gnuplot> splot '3D-data.dat' using 1:2:3 with linespoints

A single-column datafile (e.g., a time series) can also be plotted as a 2-D graph:

gnuplot> plot [-5:15] '2D-data-1col.dat' with linespoints

or as a 3-D graph (blank lines in the datafile, as above):

gnuplot> set noparametric ; set hidden3d
gnuplot> splot '3D-data-1col.dat' using 1 with linespoints

To print a graph: if the command to print on your Postscript printer is lpr -Pps file.ps, issue:

gnuplot> set term post
gnuplot> set out '| lpr -Pps'
gnuplot> replot

then type set term x11 to restore. Don't get confused---the last print will come out only when you quit gnuplot.

For more info, type help or see the examples in directory /usr/lib/gnuplot/demos/, if you have it.

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