Hi ROOTers,
I have questions concerning FFT (ROOT svn head, fftw-3.2.1, win32).
I didn't find answers neither in the ROOT nor fttw3 docs.
An macro (attached) is based on the the ROOT tutorial.
I cant figure out the following:
1. how to scale x-axis on the pad "Magnitude of the 1st transform"
in order to have "real frequency"
2. how to scale y-axis on the pad "Magnitude of the 1st transform"
in order to have "real magnitude"
3. I found that "frequency reconstruction" ("Magnitude of the 1st transform" hist)
drastically depends on the number of samples (n parameter in the macro) and range (upX). Could you recommend a procedure for their calculation? 4. I see that magnitudes of frequencies are different (but they should be equal).
How to correctly find/reconstruct magnitudes?
I posted these questions in the list because of urgency.
Please, answer to me directly or at
http://root.cern.ch/phpBB2/viewtopic.php?p=34633
Thanks.
Regards. Valeriy
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