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Article #826Re: Mystery FFT Code...
From: Miguel Oyarzun
Date: Tue, 12 Jun 1990 21:05
Date: Tue, 12 Jun 1990 21:05
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1336 bytes
In article <2846@syma.sussex.ac.uk> paulr@syma.sussex.ac.uk (Paul T Russell) writes: >This looks very much like the code from "Numerical Recipes in Pascal". >(Vetterling et al ?). The arrays consist of alternate real, complex >values and start at an indexs of 1, so array[1] = x[0].re, array[2] = >x[0].im, array[3] = x[1].re, etc... > >Incidentally, I think they have the signs for the FT and inverse FT >the wrong way round - can anyone confirm this ? > If you look at the Numerical Recipes' definition of the Fourier integral, you will see that their algorithm is consitent with their definition. Unfortunately, they selected the opposite sign convention on the complex exponential from that commonly used in engineering work :-(. I guess it's the old scientist-vs-engineer's way of looking at the world. Miguel
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arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!yale!mintaka!mit-eddie!bbn.com!moyarzunReferences:
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!yale!mintaka!mit-eddie!bbn.com!moyarzun From: moyarzun@bbn.com (Miguel Oyarzun) Newsgroups: comp.dsp Subject: Re: Mystery FFT Code... Message-ID: <57353@bbn.BBN.COM> Date: 12 Jun 90 21:05:42 GMT References: <30678@cup.portal.com> <2846@syma.sussex.ac.uk> Sender: news@bbn.com Reply-To: moyarzun@labs-n.bbn.com (Miguel Oyarzun) Organization: Bolt Beranek and Newman Inc., Cambridge MA Lines: 17