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MathGroup Archive 2012

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mListFFT[] simple FFT function for review

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125310] mListFFT[] simple FFT function for review
  • From: "McHale, Paul" <Paul.McHale at excelitas.com>
  • Date: Tue, 6 Mar 2012 05:56:21 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Purpose of this function is to take a list with {TimeOfSample,Data} pairs and perform FFT to show spectral content.  It assumes the data is evenly spaced.

I know it's simple.  Any input welcome or extra features you think would be useful.

Input: {{TimeOfSample,Data},...} pairs
Output: {{Frequency, Energy},...};

mListFFT[InputList_]:=Module[{Xaxis,Yaxis,AveragePeriod},
AveragePeriod=Plus@@Table[InputList[[i+1,1]]-InputList[[i,1]],{i,1,Length[InputList]-1}]/(Length[InputList]-1);
Xaxis=1/AveragePeriod*Range[0,Floor@(Length[InputList]/2.)-1]/Length[InputList];
Yaxis=Abs[Fourier[InputList[[All,2]]]];
Yaxis=Yaxis[[1;;Floor@(Length[Yaxis]/2.)]];
Transpose[{Xaxis,Yaxis}]
]

I am considering looking at the averaging of the time between samples to detect sample time discontinuities by looking for a maximum deviation from max time difference to min time difference.

Any input welcome.


Paul McHale  |  Electrical Engineer, Energetics Systems  |  Excelitas Technologies Corp.

Phone:   +1 937.865.3004   |   Fax:  +1 937.865.5170   |   Mobile:   +1 937.371.2828
1100 Vanguard Blvd, Miamisburg, Ohio 45342-0312 USA
Paul.McHale at Excelitas.com
www.excelitas.com



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