Hi Bryan:
On Tue, Apr 16, 2013 at 1:21 PM, Bryan Woods
I'm trying to do something that at first glance I think should be simple but I can't quite figure out how to do it. The problem is as follows:
I have a 3D grid Values[Nx, Ny, Nz]
I want to slice Values at a 2D surface in the Z dimension specified by Z_index[Nx, Ny] and return a 2D slice[Nx, Ny].
It is not as simple as Values[:,:,Z_index].
I tried this:
values.shape (4, 5, 6) coords.shape (4, 5) slice = values[:,:,coords] slice.shape (4, 5, 4, 5) slice = np.take(values, coords, axis=2) slice.shape (4, 5, 4, 5)
Obviously I could create an empty 2D slice and then fill it by using np.ndenumerate to fill it point by point by selecting values[i, j, Z_index[i, j]]. This just seems too inefficient and not very pythonic.
The following should work:
values.shape (4,5,6) coords.shape (4,5) values[np.arange(values.shape[0])[:,None], ... np.arange(values.shape[1])[None,:], ... coords].shape (4, 5)
Essentially we extract the values we want by values[I,J,K] where the indices I, J and K are each of shape (4,5) [or broadcast-able to that shape].