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MathGroup Archive 2002

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Re: FourierTransform problem

  • To: mathgroup at smc.vnet.net
  • Subject: [mg35100] Re: [mg35081] FourierTransform problem
  • From: BobHanlon at aol.com
  • Date: Tue, 25 Jun 2002 03:39:41 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 6/24/02 4:58:37 AM, dturner at faulkner.edu writes:

>I am using Mathematica for Students 3.0.1 with Windows 98.  When I execute
>the following code, I get the error messages below:
>
>In[1]:=
><<Calculus`FourierTransform`
>
>In[2]:=
>Clear[fx, fw, a]
>
>In[3]:=
>a:=1
>
>In[4]:=
>fx[x_]:=Exp[-Abs[x*a]]
>
>In[5]:=
>fw[w_]:=InverseFourierTransform[fx[x], x, w]
>
>In[6]:=
>Plot[fw[w], {w, -5*a,5*a}]
>
>Plot::plnr : fw[w] is not a machine-size real number at w = -5..
>Plot::plnr : fw[w] is not a machine-size real number at w = -4.59433..
>Plot::plnr : fw[w] is not a machine-size real number at w = -4.15191..
>General:: stop : Further output of Plot::plnr will be suppressed during
>this
>calculation.
>
>Does anyone know where I might obtain a corrected FourierTransform.m package
>for Mathematica 3.0.1?  My copy is dated 7/21/97.  I contacted Wolfram
>about
>this matter.  However, they told me they no longer support version 3.0.
> I
>appreciate any help you may provide.
>

Your example works fine with version 4; however, it would be much faster 
and might work with your version if you use Evaluate in the RHS of the 
definition of fw.

$Version

4.1 for Mac OS X (November 5, 2001)

<<Calculus`FourierTransform`

Clear[fx, fw, a]
;

a=1;

fx[x_]:=Exp[-Abs[x*a]];

fw[w_]:=Evaluate[InverseFourierTransform[fx[x], x, w]];

Plot[fw[w], {w, -5*a,5*a}];


Bob Hanlon
Chantilly, VA  USA


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