Hi, Ellen-
Thanks, I'll look at your data, but I note that the selected ROIs are not chosen randomly. This program was built to prepare taking 3dNetCorr and 3dTrackID outputs and build 3dMVM tables+commands. 3dMVM does not handles missing data across subjects (in most cases). So, the ROIs here are those ROIs where tracts were found across *all* subjects.
The above is the "intersection" of nonzero regions; the "-unionize" option puts *all* ROIs into the table, whether they have zero values or not.
--pt