griddata and masked arrays

Community matplotlib-users
1

Hi,

I am trying to use griddata to plot some (irregularly) spaced data as a
contour plot, but sometimes ALL the grid it outputs is masked: so no plot.

In the docs I read:
"A masked array is returned if any grid points are outside convex hull
defined by input data (no extrapolation is done)."

but I have no real idea of what does it mean.
Any suggestion to troubleshoot / understand what's going on?

Thanks!

m.

2

2010/4/3 ms <devicerandom@...287...>:

I am trying to use griddata to plot some (irregularly) spaced data as a
contour plot, but sometimes ALL the grid it outputs is masked: so no plot.

In the docs I read:
"A masked array is returned if any grid points are outside convex hull
defined by input data (no extrapolation is done)."

but I have no real idea of what does it mean.
Any suggestion to troubleshoot / understand what's going on?

When you do trinangulation, the lines between all pairs of points
define an inner region and an outer region, I guess, the inner region
is meant by "outside convex hull".

I furthermore guess, that all your interpolation points are outside
this hull, i.e., your interpolation spacing is of comparable order of
magnitude as your input data extent?

Friedrich