Figure 3

Plotting a surface.

mundook{160}% gnuplot
        G N U P L O T
        unix version 3.5
        patchlevel, 27 Aug 93
        last modified Fri Aug 27 
05:21:33 GMT 1993
        Copyright(C) 1986 - 1993   
Thomas Williams, Colin Kelley
        Send comments and requests for 
help to 
        Send bugs, suggestions and mods 
Terminal type set to 'x11'
gnuplot> set term pbm color
Terminal type set to 'pbm'
Options are 'small color'
gnuplot> set output "test2.ppm"
gnuplot> set hidden3d
gnuplot> splot [-3:3] [-3:3]  
gnuplot> quit
mundook{161}% ppmtogif test2.
ppm > test2.gif 
ppmtogif: computing colormap...
ppmtogif: 4 colors found