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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:

with(inttrans):
plot(2*Pi*invfourier((sin(x*Pi)/(x*Pi)*(2*cos(Pi*x)+cos(3*Pi*x)
-(I)*(2*sin(Pi*x)+sin(3*Pi*x)))),x,t),t=-20..20);

In Mathmatica:

Y[t_]:=InverseFourierTransform[(Sin[w*Pi]/(Pi*w))*(2*Cos[Pi*w]+Cos[Pi*w*3]-I*(2*Sin[Pi*w]+Sin[3*Pi*w]),w,t]

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
>
>
> 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
> http://www-astro.unice.fr/PagePerso/aristidi/

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