Re: Fourier transform
- To: mathgroup at smc.vnet.net
- Subject: [mg13928] Re: [mg13923] Fourier transform
- From: "Jens-Peer Kuska" <kuska at linmpi.mpg.de>
- Date: Tue, 8 Sep 1998 02:52:28 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Hi Andrea,
Fourier[] implements a numerical fast fourier transform. That means that
the data passed to Fourier[] are the function values f(t) on the
interval t in [0,2Pi) with constant increment. The data are assumed to
be periodic in t with period 2Pi.
Assume You have a solution ndsol={y[t]->InterpolatingFunction[<>][t]}
With
fun=y[t] /. ndsol;
pointNo=256;
inc=N[2Pi]/(pointNo-1);
data=Table[fun,{t,0.,2.*Pi,inc}];
You get Your data set and can use
fftdata=Fourier[data]
to make the transformation.
For other time intervals You need a proper scaleing of the t-variable.
Hope that helps
Jens
-----Original Message-----
From: Andrea Cherubini <Andrea.Cherubini at roma1.infn.it> To:
mathgroup at smc.vnet.net
Subject: [mg13928] [mg13923] Fourier transform
>Hello,
>
>how can I do the Fourier Transform of NDSolve results?
>
>Thanks, Andrea
>
>
>