I installed octave and not only did it not work, but it destroyed my
installation of cygwin.
Officially, octave supposedly uses a specially built version of cygwin
that doesn't share registry entries with regular cygwin, but that
clearly isn't the case. I've been told that there is a version of
Octave built to run in your preexisting cygwin installation so I guess
that's what I should have installed.
Anyway my point is that Octave is a can of worms with serious
installation problems.