Re: mListFFT[] simple FFT function for review
- To: mathgroup at smc.vnet.net
- Subject: [mg125338] Re: mListFFT[] simple FFT function for review
- From: Dana DeLouis <dana2010 at me.com>
- Date: Wed, 7 Mar 2012 05:38:29 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
Hi. Not sure if this helps...
Symbolic data (x,y) pairs:
v=Array[x,{4,2}];
Your equation for AveragePeriod:
AveragePeriod=Plus@@Table[v[[i+1,1]]-v[[i,1]],{i,1,Length[v]-1}]/(Length[v]-1)
(1/3) * (x[4,1] - x[1,1])
Mean[Differences[v[[All,1]]]]
(1/3) * (x[4, 1] - x[1, 1])
%% == %
True
Which would be true with your statement --It assumes the data is evenly spaced.--
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HTH :>0
Dana DeLouis
Mac & Math 8
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On Mar 6, 5:57 am, "McHale, Paul" <Paul.McH... at excelitas.com> wrote:
> 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[I nputList]-1}]/(Length[InputList]-1);
> Xaxis=1/AveragePeriod*Range[0,Floor@(Length[InputList]/2.)-1]/Length[InputL ist];
> 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.McH... at Excelitas.comwww.excelitas.com
>
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