Re: fourier transform

*To*: mathgroup at smc.vnet.net*Subject*: [mg61238] Re: [mg61203] fourier transform*From*: Pratik Desai <pdesai1 at umbc.edu>*Date*: Thu, 13 Oct 2005 01:39:46 -0400 (EDT)*References*: <200510120543.BAA09326@smc.vnet.net> <434DCA7B.3070004@umbc.edu>*Sender*: owner-wri-mathgroup at wolfram.com

Pratik Desai wrote: > 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) >> >> > It should give you complex numbers, that is the whole idea of Fourier > Transform ( I think :-\ ) > You can find the amplitude(frequency domain Frequency Response > Function) simply by taking the absolute value and plotting it with > respect to the number of points, and obviously the phase is given by > taking Arg. I may be wrong about this but I don't think the way you > have constructed your input list will work, the best way is to do is > to construct your list with only amplitudes with a suitable time step. > To gurantee good results the number of points should be something > like 2^n ;-) .....256, 512, 1024 etc. > >> >> Any help appreciated. >> >> thanks >> >> > Hope this helps > > > Pratik . > You can find more information on this in the Mathematica Book 3.8.4 Just type 3.8.4 in help browser in Mathematica -- Pratik Desai Graduate Student UMBC Department of Mechanical Engineering Phone: 410 455 8134

**References**:**fourier transform***From:*Masrur Hossain <Lessjunk@yahoo.com>