Le Mon, 29 Mar 2010 16:12:56 -0600, Charles R Harris <[email protected]> a écrit :
> On Mon, Mar 29, 2010 at 3:00 PM, Pascal <[email protected]> wrote: > > > 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 <k, x>, 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 <k, Ox> = <O.T, x>. 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 _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
