[Freesurfer] About the pdf_gamma function in fsfast's toolbox

Hi,   I’m working on some fMRI data processing these days. In order to construct a HRF, I find this Matlab function in fsfast. But after some careful comparison, it seems that the gamma pdf in this function is not consistent with FSL’s version, and differs from the standard gamma pdf. So perhaps it is a typo in your code?   In this function, the gamma pdf is written as:

pdfx = (b.^2) .* (…);

But comparing to FSL’s feat_model.cc, I think this term should be

pdfx = (b.^a) .*(…);

Which will be consistent with the original gamma pdf from Wikipedia.   Thanks for your nice software and thanks for your attention. 😊   Su, ---

From Beijing Normal University.