afni.nimh.nih.gov

Not at this time. The only way to do that would be to use 3dExtractGroupInCorr to break individual datasets out of the .niml/.data files, then reassemble the subset you like with 3dSetupGroupInCorr.

I can consider adding this subset capability as an option, but I don't know when I will get around to it. I am glad to hear someone using 3dGroupInCorr, since it doesn't seem to get much love, and I feel it is a nice tool. Of course, I wrote it, so I'm biased that way.