griddata runtime error — Python / SciPy (Interpolation)

Question

I use scipy\'s griddate-function for interpolation.

What does the following error message means which appears when python is executing the griddata-function?

Answer 1

This typically means that the point set you passed in cannot be triangulated. Some common cases when this might occur:

• You have 2D data, but all the points lie along a line. In this case there is no triangulation of the data to non-degenerate triangles.
• You have 3D data, but all the points lie on a plane, so no decomposition to non-degenerate tetrahedra. And so on to higher dimensions.

In these cases, interpolation does not make sense either, so this failure is not an indication of a bug, but incorrect usage of griddata.

Typically, Qhull prints additional information on what went wrong to stderr, so check the program output to see what it says.

Answer 2

This indicates that the qhull (http://www.qhull.org) code which is used by the function is not returning a result because of an error.

Does this always happen, or only for certain inputs?

Can you post an example input which causes the error?