Hi, Kate-
OK, I asked The Bob a bit more about this program, and he mentioned that @grayplot script is specifically made to partner with afni_proc.py output-- for most applications, this means that the relevant files to plot will be *+tlrc.BRIK/HEAD files; there will also be other things present to add to the plots. To do this, the @grayplot script has some hardwired features (e.g., the "tlrc" space assumption).
If you just want to make grayplots of a given time series file in a more general context, you can go to the source program, 3dGrayplot, which @grayplot utilizes:
[
afni.nimh.nih.gov]
One or the other might be easier for a given usage case.
--pt