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Re: Fourier frequencies

  • To: mathgroup at
  • Subject: [mg43428] Re: [mg43401] Fourier frequencies
  • From: Sseziwa Mukasa <mukasa at>
  • Date: Wed, 17 Sep 2003 07:58:44 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

On Friday, August 29, 2003, at 07:16 AM, akpovo wrote:

> Hello to all,
> How possible is it to compute a fourier transform of a data set {t,x}  
> in
> order to have the fourier coefficient and the corresponding frequency?
> Tahnks

The Fourier Transform is computed as normal


Traditionally the 0 frequency is placed in the center of the spectrum,  
after an FFT though it is at the left so we rotate the data:


The frequencies are determined from the time with the following function


You can the use ListPlot to get the spectrum, assuming the data is in  
the list x and the times in the list t




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