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Re: inverse fourier transfrom ifft problem, need help

From: eric
Subject: Re: inverse fourier transfrom ifft problem, need help
Date: Tue, 07 Mar 2000 11:01:53 -0900

Dear matlab camp expert:

    I solve and succesfully plot it on mapleV5 for linux and
mathmatica4.0 for windows
in maple:


In Mathmatica:


Plot[Y[t],{t, -20, 20}];

Do any one know the how to tranport the math type formula written either
by microsoft word or Applixware to IE5 or netscape4.6?  I did one on IE5
from MSword97, but now I forget how to, need your help

Tell two example on maple and mathmatica is not mean I lose interest on
matlab or octave.
rather we should can utilize the public tool to communicate our contuor
or direction of ideas easily,

so I tried to change your suggestion f=-32:0.25:32, but the result still
be oscolated around 0 rather than a rectangular kind's shape y=2 0<x<1,
y=1 1<x<2;  y=0 x>2 that's what maple and mathmatica proved to me.


Eric Aristidi wrote:
> Hello,
> There are some error in your code :
> > f=-128:128;
> ... maybe frequency is too high (too many oscillations in the sin,
> causing maybe an undersampling), I would have tried f=-32:0.25:32
> >
> > y=((sin(pi*f)/(pi*f)))
> ... sin(pi*f) is a vector, pi*f also, so the "/" is a vector operation
> (I don't know what does exactly means to divide a vector by another...).
> You should type
> y=(sin(pi.*f)./(pi.*f)) instead
> and
> y(129)=1 to avoid singulary at zero.
> also remember that the origin on a FFT operation is at point N/2+1 ; a
> 1-pixel on the signal shift causes imaginary part to appear even is the
> Fourier Transform is real. (I always plot the modulus).
> Hope it helps
> Eric
> --
> Eric Aristidi
> Dpt Astrophysique - Universite de Nice, Parc Valrose, 06108 Nice Cedex 2
> mail   : address@hidden
> fax    : +33 4 92 07 63 21
> phone  : +33 4 92 07 63 45

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