Re: fourier transform

*To*: mathgroup at smc.vnet.net*Subject*: [mg61214] Re: fourier transform*From*: Torsten Coym <torsten.coym at eas.iis.fraunhofer.de>*Date*: Thu, 13 Oct 2005 01:39:25 -0400 (EDT)*Organization*: Fraunhofer Gesellschaft (http://www.fraunhofer.de/)*References*: <dii9qs$9q1$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Take a look at Mathematica's help: Fourier[data] expects data to be a list of complex numbers, not pairs of time and amplitude. I assume that your list is equally spaced in time -- only then a application of Fourier[] would lead to useful results. Get rid of the timing information in your data, by replacing every pair of {time,amplitude} with the amplitude only. data=yourdata/.{t_,ampl_}->ampl freqdata=Chop@Fourier[data] Have a look at Chop[] to suppress small imaginery parts that come from the numerical process. Cheers, Torsten Masrur Hossain wrote: > Hi folks > I have a list of pairs of numbers like > > {{1.2, 3.4}, {2.2, 3.6}............} > The first part is time and second part is amplitude. > > when I do the fourier transform by using > Fourier[list] > > it gives me list of complex numbers but I expect real numbers > (i.e . amplitude versus frequency) > > > Any help appreciated. > > thanks