Example of how to create and save a polar plot

gnuplot> set polar
gnuplot> set samples 5000
gnuplot> l=2               
gnuplot> p=0.
gnuplot> plot cos(l*t+p)**2
gnuplot> p=.25 
gnuplot> p=pi/2
gnuplot> replot
gnuplot> set terminal postscript color
Terminal type set to 'postscript'
Options are 'landscape noenhanced color dashed defaultplex "Helvetica" 14'
gnuplot> set output "plot.ps"
gnuplot> replot
gnuplot> exit