
From:  Roberto Hernandez 
Subject:  Re: A question on fftshift 
Date:  Sun, 21 Jul 2002 20:16:04 0300 
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Steve M. Robbins wrote:
is that the frequency interval for the FFT output is [fc,fc] where fc is the critical (Nyquist) frequency.For an odd number of samples. Otherwise it's [fc, fc  1(N*Dt)].No, the samples are equallyspaced around the unit circle, with a sample always at angle zero. So you'll only get a sample halfway around (at frequency +/ fc) if N is even.
You're right, but that's not what I was referring to. If you have an even number of samples then the FFT output bins will not be on a symmetrical frequency interval [fc, fc], rather [fc, fc  1/(N*Dt)] where fc=fs/2. OTOH, if N is odd, the frequency interval will be symmetrical: [fa, fa] where fa=(N1)*fs/(2*N).
Thanks for the patch. Regards, Roberto  Octave is freely available under the terms of the GNU GPL. Octave's home on the web: http://www.octave.org How to fund new projects: http://www.octave.org/funding.html Subscription information: http://www.octave.org/archive.html 
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