Re: FourierTransform Bug V4
- To: mathgroup at smc.vnet.net
- Subject: [mg20553] Re: FourierTransform Bug V4
- From: Jane.M.Manderscheid at lerc.nasa.gov (Jane M Manderscheid)
- Date: Sat, 30 Oct 1999 00:14:04 -0400
- Organization: NASA Lewis Research Center
- References: <7v3dqn$64d@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
I don't know how to fix it, but the problem may be due to the usage of
DiracDelta functions rather than Fourier transforms. Try the following
command:
Integrate[2 DiracDelta[w-2x],x]
-1+UnitStep[-w+2 x]
Change the w to y and you'll get a different answer:
Integrate[ 2 DiracDelta[y-2 x],x]
UnitStep[2 x-y]
These results were obtained from V. 4 on unix platforms. Version 3 works
correctly. I emailed Wolfram a week ago but have not received a response.
Jane Manderscheid
NASA Glenn Research Center
In article <7v3dqn$64d at smc.vnet.net>, lwalker701 at earthlink.net says...
>
>FourierTransform of v4 returns incorrect values. For
>example, the following is computed in version 4:
>
>FourierTransform[UnitStep[t], t, w, FourierParameters ->
>{1,-1}]
>
>= -(I/w) - Pi*DiracDelta[w]
>
>But version 3 correctly returns
>
>-(I/w) + Pi*DiracDelta[w]
>
>How can I fix this? Perhaps Unprotect[FourierTransform]...
>
>Thanks,
>Lawrence
>
>
>--
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> Lawrence A. Walker Jr., M.Eng./Ph.D. Candidate
> Morgan State University
> Clarence M. Mitchell School of Engineering
> COMSARE (Center Of Microwave/Satellite And RF Engineering)
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