Hey,
I have looked into both codes (
3dRSFC and DPABI's
y_alff_falff.m, version 6.1).
I think the relevant line in DPABI y_alff_falff.m is 139:
AllVolume(:,Segment) = 2*abs(fft(AllVolume(:,Segment)))/sampleLength;
with AllVolume being the reshaped to 2D, masked, detrended, and zero-padded 4D input time series (Segment is an option to separate data into junks to be more RAM memory friendly; can be ignored here)
and sampleLength being the number of time points.
Next, ALFF_2D is calculated as:
ALFF_2D = mean(AllVolume(idx_LowCutoff:idx_HighCutoff,:));
As I am not really familiar with C, I did not fully understand whether this method is different compared to 3dRSFC (and the relevant lines of code starting from line 725). Could you maybe explain that a bit more?
Best, Melissa
