Hello,

I'm implementing a PLPlot software interface for a finite element library. The PLPlot package works great so far! Unfortunately I encountered a problem concerning contour plots of scalar value functions:

The FE mesh is unstructured, i.e. there is no rectangular grid of points for which a scalar value is known. Therefore I used the pltr2-parameter to display a N-times-1 degenerated grid which is in fact a list of all available FE grid points. This method has already worked for PLPlot vector plots, but, alas, not for contour plots. I received the message

plfcont: indices must satisfy 1 <= ky <= ly <= ny

which is generated in src/plcont.c, line 500, after I had made the call

plcont(z, nx, ny, 1, nx, 1, ny, clevel, nlevel, pltr2,(void *)&cgrid2);

where nx=N, ny=1.

The above condition is satisfied (trivially), so I am not sure if this is a programming bug in the PLPlot package or if I have overseen another point. By the way: Is there a more clever way to solve my task?

Florian