[vtk-developers] Inconsistency in numpy_support

[Prabhu Ramachandran]

Hi Berk,

Berk Geveci wrote:
> I have been playing around with numpy-vtk array conversion. I think
> there is an inconsistency in the way numpy_support converts VTK arrays
> to numpy arrays. If the array has 1 component, vtk_to_numpy returns an
> array of shape (10,), whereas if the array has 3 components,
> vtk_to_numpy returns an array of shape (10,3). This makes the
> following impossible
> 
> vtk_to_numpy(scalar) + vtk_to_numpy(vector)

Try this:

vtk_to_numpy(scalar)[:,None] + vtk_to_numpy(vector)

This is the way to broadcast the 1D array so the addition is possible.

> Shouldn't  vtk_to_numpy return an array of shape (10,1) when converting scalars?

Not really since a (10,1) array is like a column vector.  If you did

  x = linspace(0, 10)

you end up with an array with shape (50,) and not (50,1) so it seems 
more natural to return a 1 component array with 10 elements as a (10,) 
shape array.

> Happy new year!

Thanks!  Wishing you the same!

cheers,
prabhu