GUI for Understanding Nyquist Plots

This program is a GUI that starts with a transfer function, and then displays the evolution of the Nyquist plot, including excursions around poles on the jw axis. It shows the path in "s" and in "G(s)H(s)" including places where the plots go to infinity (this is missing from Matlab's "nyquist" command, and can cause confusion).

When the plot is done, an explanation is given about why the system is shown to be stable or unstable.

The program is meant to me a learning tool, not a general tool for making Nyquist plots (Matlab's "nyquist" command already does that well).

Full Description at:
http://lpsa.swarthmore.edu/Nyquist/NyquistGui.html

More information at:
http://lpsa.swarthmore.edu/Nyquist/Nyquist.html

As it stands the commenting is poor, but if you have problems, please contact me (echeeve1@swarthmore.edu).