My software demos are written in gnuplot, octave and matlab. I will put the source code here.
Unfortunately, matlab is not free software. If your college
does not have it,
(a) ask them to get it [and tell them
that 50 licenses are cheaper than 6];
(b) ask an engineer
friend to let you use theirs [all engineers use it].
> load 'gnu' # (or whatever the filename is for the demo)