this implements a filled contour function (contourf.m). It depends on the revised __contourc__.cc patch. Further on the inpolygon.m function from octave-forge is needed.
Please note contourf.m and inpolygon.m depend on octave functions (e.g. false(n) + size_equal(X,Y) )not available for 2.1.73 cygwin. So, I am not sure what to do about this issue.