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MathGroup Archive 1999

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Re: Problem with the zero-term of Fourier[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19642] Re: Problem with the zero-term of Fourier[]
  • From: hans.steffani at e-technik.tu-chemnitz.de (Hans Steffani)
  • Date: Tue, 7 Sep 1999 00:28:37 -0400
  • Organization: Chemnitz University of Technology, GER
  • References: <7qsftj$17c@smc.vnet.net> <7qvu1p$4o2@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Paul Abbott <paul at physics.uwa.edu.au> writes:

>Hans Steffani wrote:

>> If have a long list of measured values in ixr.
>> (Plus@@ixr)/Sqrt[Length[ixr]]
>> gives
>> -146.263
>>
>> but
>> Fourier[ixr][[1]]
>> gives
>> -56.1317-3.03437 I
>>
>> which is complex although it should be real (ixr is a list of
>> real numbers) and it is different from the first term althugh
>> it should be the same.

>Assuming that ixr is real then I can only guess that the problem
>arises from the bug with packed arrays of complex numbers?

Sorry, what do you mean with "packed arrays of complex number"?

I'm am sorry that I do not have a simple example; maybe you want
analyze me measuered data , but I am not sure about ;)

h.f.s.
--
Hans Friedrich Steffani
Institut fuer Elektrische Maschinen und Antriebe, TU Chemnitz
mailto:hans.steffani at e-technik.tu-chemnitz.de
http://www.tu-chemnitz.de/~hfst/


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