freqanalysis_wltconvol.m question

Brian Roach Brian.Roach at YALE.EDU
Wed Nov 8 21:20:10 CET 2006


In the freqanalysis_wltconvol.m function, the FFT of zero-padded eeg or MEG
data and the FFT of the wavelets at various frequencies of interest are
convolved and the inverse FFT of that result is used to calculate power in
this manner on line 283:
powdum = (2.* abs(autspctrmacttap)  ./ data.fsample) .^ 2;
here, autspctrmacttap corresponds to the complex output from the call to
In previous e-mail Jan-Mathijs has mentioned that the abs of the complex
data gets you amplitude, so I am wondering why it gets multiplied by 2 and
divided by the sampling rate before being squared since power =
amplitude^2.  I am wondering how important it is to multiply by 2 and
divide by the AD rate because I would like to take this complex output and
use it to calculate phase-locking factor, but I am not sure what parts of
the power transformation need to be removed - just the abs() and the
squaring?  Clarification of this line of code would be extremely helpful to me.

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