[SciPy-user] wavevector arrays

[J Oishi]

Hi,

I am performing a number of 3D FFTs using scipy, and I had a question  
as to how to setup 3 3D arrays of wavevectors, much like one might do  
with mgrid. However, because the FFT returns wavevectors running from  
0,...,k_c, -k_c, ..., -1 (where k_c is the nyquist wavenumber) I'm  
not sure how to get mgrid to do this.

In 2D, I could create two 1D kx and ky arrays and use meshgrid (for  
an even number of points):

import numpy as N

kx = 2*N.pi/Lx * N.concatenate(N.arange(0,nx/2-1),N.arange(-nx/2, 0))
ky = 2*N.pi/Ly * N.concatenate(N.arange(0,ny/2-1),N.arange(-ny/2, 0))

kk = meshgrid(kx,ky)

where kk would have a shape (2,ny,nx). However, this (to my  
knowledge) doesn't generalize to 3D.

I'm a total python/scipy neophyte, so any help you could provide  
would be quite appreciated.

thanks,

jeff