Gnuplot

From NA-Wiki

Gnuplot makes it very easy to produce nice looking eps plots from the numerical output of your simulation. A good starting points is the following snippet. Either type it in on the gnuplot prompt, or save it in a file and run it from gnuplot with load "file.p".

set terminal postscript enhanced color size 5,4 "Helvetica,10"
set out "test.eps"
set pointsize 2
set border linewidth 0.5
unset key
set title "Some plot"
set xlabel "{/Symbol s}"
set ylabel "field"
plot "data1d.txt" with points, \
     "data1d.txt" smooth csplines with lines

This reads the data in data1d.txt and plots it to test.eps. The size is set to 5x4 inches.