I tried to get example x21c to work properly on
Windows, using the CSA library. Unfortunately it returns
only zero values as interpolation results.
In the process I noticed that some of the other methods
rely on the index array to have been filled before!
For instance: grid_nnaidw() uses the (static) array
"index" to determine the neighbours, but the function
that fills that array (either dist1() or dist2()) is not called
in that routine.
Arjen, please close this bug report if the problem has been fixed for modern PLplot.