new function: zgrid.m

[Tarmigan Casebolt]

Hi,

I've written (and attached) a version of the function zgrid.m.  This
function is used to plot contour lines for zeta and omega_n on a root
locus plot.  This can be helpful when viewing root locus plots and
doing control design.  Please run the demo for an example.  (The demo
works best with a bug fix that JWE posted to the bugs list earlier
today).

Please let me know what changes I might be able to make to have it be
accepted into octave.  In matlab, zgrid is part of the Control Systems
Toolbox, which I believe always gets installed (or maybe that's only
with the academic versions?)

I also have an sgrid.m that is almost ready to send, but it's a bit
messier, so I'll wait to send to hear what cleanups might be needed
for this one.

Thanks,
Tarm

zgrid.m
Description: Binary data