Dear All,

In the help
information for the FFT function I find that, regarding the
"inverse" FFT, fft(x,1), the formula is

n

x(k) = SUM(a(m)*exp(2*%i*%pi*(m-1)*(k-1)/n)

m=1

But this is not the inverse FFT since it lacks the required 1/n
factor; however, fft(fft(a,-1),1) indeed returns a. So the
procedure seems to be mistakenly described in the help
information.

Interestingly, the fftw3 documentation, http://www.fftw.org/fftw3.pdf,
gives, on page 42, the same formula but it indicates it is an
unnormalized transform.

Would you please clarify?

Regards,

Federico Miyara
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