[Numpy-discussion] Normalization of ifft

Lutz Maibaum lutz.maibaum@gmail....
Thu Mar 26 18:56:13 CDT 2009


Hello,

I just started to use python and numpy for some numerical analysis. I
have a question about the definition of the inverse Fourier transform.
The user gives the formula (p.180)

  x[m] = Sum_k X[k] exp(j 2pi k m / n)

where X[k] are the Fourier coefficients, and n is the length of the arrays.

The online documentation
(http://docs.scipy.org/doc/numpy/reference/routines.fft.html), on the
other hand, states that there is an additional factor of 1/n, which is
required to make ifft() the inverse of fft(). Is this a misprint in
the user guide?

  Lutz


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