Problem with the zero-term of Fourier[]
- To: mathgroup at smc.vnet.net
- Subject: [mg19606] Problem with the zero-term of Fourier[]
- From: hans.steffani at e-technik.tu-chemnitz.de (Hans Steffani)
- Date: Sat, 4 Sep 1999 21:09:14 -0400
- Organization: Chemnitz University of Technology, GER
- Sender: owner-wri-mathgroup at wolfram.com
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.
I also tried
1/Sqrt[Length[ixr]] *
Sum[ixr[[tau]] Exp[2 Pi I(tau-1)(1-1)/Length[ixr]],{tau,Length[ixr]}]
which also gives -146.263
What is the problem?
Hans Friedrich Steffani
--
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/