Question on Freqanalysis_tfr

[Paco Diaz]

Dear fieldtrip users,

  While reading carefully what the function freqanalysis_tfr do, I have
found something that seems very extrange to me. I think that the general
procedure for the wavelet transformation is clear but I can't get why do you
multiply by 2, and divide by the sampling rate, the absolute value of the
convolution.
  I have still used the function with very good results, but I would like to
understand that step in order to sleep well.

Here is a piece of the code:

  for k=1:size(dat,1)
    for j=1:length(cfg.foi)
      cTmp = conv(dat(k,:),M{j});
      cTmp = (2*abs(cTmp)/data.fsample).^2;
      cTmp = cTmp(ceil(length(M{j})/2):length(cTmp)-floor(length(M{j})/2));
      cTmp = cTmp(:,1:cfg.downsample:end);
      if strcmp(cfg.keeptrials, 'yes')
        freq.powspctrm(i,k,j,:) = cTmp';
      else
        freq.powspctrm(k,j,:) = squeeze(freq.powspctrm(k,j,:)) + cTmp';  %
compute the running sum
      end
    end
  end


Thank you very much in advance, Paco.

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