[Scilab-users] Possible error in manual

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fmiyara fmiyara
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[Scilab-users] Possible error in manual


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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