Le Mon, 29 Mar 2010 16:12:56 -0600, Charles R Harris a écrit :

On Mon, Mar 29, 2010 at 3:00 PM, Pascal wrote:

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Hi,

Does anyone have an idea how fft functions are implemented? Is it pure python? based on BLAS/LAPACK? or is it using fftw?

I successfully used numpy.fft in 3D. I would like to know if I can calculate a specific a plane using the numpy.fft.

I have in 3D: r(x, y, z)=\sum_h^N-1 \sum_k^M-1 \sum_l^O-1 f_{hkl} \exp(-2\pi \i (hx/N+ky/M+lz/O))

So for the plane, z is no longer independant. I need to solve the system: ax+by+cz+d=0 r(x, y, z)=\sum_h^N-1 \sum_k^M-1 \sum_l^O-1 f_{hkl} \exp(-2\pi \i (hx/N+ky/M+lz/O))

Do you think it's possible to use numpy.fft for this?

I'm not clear on what you want to do here, but note that the term in the in the exponent is of the form , i.e., the inner product of the vectors k and x. So if you rotate x by O so that the plane is defined by z = 0, then = . That is, you can apply the transpose of the rotation to the result of the fft.

In other words, z is no longer independent but depends on x and y. Apparently, nobody is calculating the exact plane but they are making a slice in the 3D grid and doing some interpolation. However, your answer really help me on something completely different :) Thanks, Pascal