Hi Peter, Thank you very much. I think this should be somewhere in the manual and the documentation. The scaling factor of the F. transform and its inverse differs a lot from discipline to discipline, so it is better to always state it explicitly.
JPi On Tue, Sep 21, 2010 at 12:39 PM, Peter L. Soendergaard <[email protected]> wrote: > tir, 21 09 2010 kl. 10:31 +0200, skrev JuanPi: >> Hi everybody, >> >> According to FFTW >> http://www.fftw.org/faq/section3.html#whyscaled >> >> the fft is not normalized...hence ifft(fft(y)) = length(y)*y > To clear things up: > > The fft is not normalized, but the ifft is normalized in such a way that > ifft(fft(y)) == y > > In FFTW, ifft is not normalized this way, so ifft in FFTW and > Octave/Matlab differs, but the fft's are the same. > > Normally, if one talks about a normalized fft, the normalization is > fft(y)/sqrt(length(y)). This gives fft and ifft the same normalization > > /Peter > > -- JuanPi Carbajal ----- "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco ----- www.ailab.ch/carbajal ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing. http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Octave-dev mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/octave-dev
