Re: plotting fourier amplitude versus frequency
- To: mathgroup at smc.vnet.net
- Subject: [mg80235] Re: plotting fourier amplitude versus frequency
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 15 Aug 2007 04:21:27 -0400 (EDT)
- Organization: Uni Leipzig
- References: <f9s4fk$atf$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
Hi, for a discrete Fourier transform of a data set of length K, the frequencies of the entry i is (i-1) 2Pi/K Regards Jens Indrani Sinha wrote: > Hi, > > I am trying to extract frequencies from a data set of > length versus time. > > Dataset: > time bondlength > > I am using the following script: > data = ReadList["length.dat",{Number,Number}]; > plain=N[Transpose[data][[2]]]; > f=Fourier[plain]; > s=OpenWrite["fourier_tmp.dat"]; > WriteString[s,"#"]; > Do[Write[s,Abs[f[[i]]]],{i,1,Length[f]}]; > Close[s]; > !sed 's/*\^/e/g' fourier_tmp.dat > cfourier.dat > Quit > > This gives me an output file cfourier.dat with the > fourier amplitude values, but how do I get the > corresponding frequencies? > > Also the first line in the output has a number; what > does that signify? > > Thank you very much, > Indrani > > > > ____________________________________________________________________________________ > Luggage? GPS? Comic books? > Check out fitting gifts for grads at Yahoo! Search > http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz >