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MathGroup Archive 2004

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Re: fourier ( FFT )

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52103] Re: [mg52077] fourier ( FFT )
  • From: yehuda ben-shimol <benshimo at bgu.ac.il>
  • Date: Thu, 11 Nov 2004 04:52:02 -0500 (EST)
  • References: <200411100945.EAA11193@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I assume the followings:
1) you already have a list of pairs such as 
myData={{x1,f[x1]},{x2,f[x2]},...}
2) x2-x1=x3-x2=..., that is, equal spaced samples.
 
under this all you need to do is to take the last value of each pair and 
use Fourier
Fourier[Last /@ myData]
will do the trick.
 
yehuda
 


bar at ANTYSPAM.ap.krakow.pl wrote:

>Hi
>
>My file has form:
>x1  f(x1)
>x2  f(x2) ....
>
>How can I use Mathematica to obtain frequencies ?
>
>Fourier[] works on only one list!
>
>When i tested with f(x)=Sin[a x] sometimes 
>i obtained wrong result.
>
>
>regards, Olaf
>
>  
>


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