Re: Help about the Fourier transform command

*To*: mathgroup at smc.vnet.net*Subject*: [mg2086] Re: Help about the Fourier transform command*From*: rknapp (Robert Knapp)*Date*: Fri, 29 Sep 1995 01:13:28 -0400*Organization*: The Santa Fe Institute

In article <DFCFHF.KtF at wri.com> Julien Soulhat <soulhat at grbb.polymtl.ca> writes: > Hello every body, > > I need help about the Fourier transform (see p.679 of the mathematica > manual). I would like to know about the following things: > > - the mathematica definition of the Fourier transform, The definition is given there on page 679: let a be a list, and n = Length[a]; Fourier[a][[s]] = b[[s]] = (1/Sqrt[n]) Sum[a[[r]] Exp[2 Pi I (r -1)(s-1)/n],{r,1,n}] similarily InverseFourier[b][[r]] = a[[r]] = (1/Sqrt[n]) Sum[b[[s]] Exp[-2 Pi I (r -1)(s-1)/n],{r,1,n}] The transform is done using the Fast Fourier Transform. > - the method for analysing datas with the Fourier transform There are so many uses of the discrete Fourier transform in data analysis that list a few here would be of little use. I am sure you can find volumes and volumes on the subject in any scientific library. Rob Knapp WRI