Re: A question on fftshift

[Roberto Hernandez]

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 equally-spaced 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=(N-1)*fs/(2*N).

Thanks for the patch.

Regards,
Roberto



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