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 FFT on a series of data sets		  New Topic  Reply to Topic
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espenhjo

Norway
20 Posts
Posted - 02/10/2004 :  06:39:12 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi all!
I need to do an FFT on a series of datasets, all having the same structure. For this have I tried to use the LabTalk script in the help file. The thing is that when I use this I don't get the correct FFT as when I select the FFT manually from the analysis menu in Origin. I use exactly the same parameters manually as in this script:

loop (i,1,9) {
fft.reset();
fft.forward = 1;
fft.forward.timeData$ = ekko00$(i)_A;
fft.forward.tdelta = 2e-6;
fft.forward.realData$ = ekko00$(i)_B;
fft.forward.imagData$ = ekko00$(i)_C
window -t W fft FFT00$(i)$;
fft.output.samplingdata$ = FFT00$(i)_Freq;
fft.output.realdata$ = FFT00$(i)_Real;
fft.output.imagdata$ = FFT00$(i)_Imag;
fft.output.ampdata$ = FFT00$(i)_r;
fft.output.phasedata$ = FFT00$(i)_Phi;
fft.output.powerdata$ = FFT00$(i)_Power;
fft.start = 1;
fft.real = 1;
fft.normalize = 1;
fft.shifted = 1;
fft.windowing = 1;
fft.spectrum = 1;
fft.unwrap = 1;
fft.convention = 1;
fft.chkres();
fft.forward();
window -t P fftplot FFT00$(i)g;
}

Any idea what could be wrong?

Regards,
Espen

Mike Buess

USA
3037 Posts
Posted - 02/10/2004 :  08:14:02 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Espen,

Although the LabTalk FFT object works fine I have always found it to be much more complicated than is necessary for a simple FFT. If you're using Origin 7.0 or later I strongly suggest that you use the OriginC FFT function instead. But the only thing that I see wrong with your script is that fft.real should probably be zero since the input data are complex.

Mike Buess
Origin WebRing Member

Edited by - Mike Buess on 02/10/2004 08:22:38 AM
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