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Re: Fourier Transform [message #74132 is a reply to message #45093]

Tue, 21 December 2010 11:51

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article
<0976cc7b-4c34-4355-aa06-1cc52757cbe7@o14g2000yqe.googlegroups.com>,
Ammar Yusuf <amyusuf1@gmail.com> wrote:

> Hi, let's say I have 2 graphs (2 arrays with numbers). They both look
> different but are similar. I'm doing a FFT on one of the arrays and
> then zero out some of the coefficients and then do an inverse FFT on
> that array to try to get the 2nd array. When I plot the 2nd array and
> the inverse one I get something similar to it but not close enough.
> I've tried zeroing many coefficients but can't get anywhere. What
> would be the best way to do this? Thanks.

Do FFTs of both arrays and compare the coefficients. If you change
the coefficients of the first FFT to match the coefficients of the
second FFT and then inverse FFT, you will get something that is
*very* similar to the second function. ;-)

But seriously, compare the coefficients from the FFTs. That will
tell you the difference between the two functions in the spectral domain.

Ken Bowman

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[Message index]

		fourier transform By: Pravesh on Mon, 01 August 2005 08:16
		Re: Fourier Transform By: R.G.Stockwell on Thu, 23 December 2010 14:15
		Re: Fourier Transform By: Ammar Yusuf on Tue, 21 December 2010 14:27
		Re: Fourier Transform By: Kenneth P. Bowman on Tue, 21 December 2010 11:51
		Re: Fourier Transform By: pgrigis on Tue, 21 December 2010 11:55

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