Paul,
Ohhhhh. Thank you for explaining the gestalt of the associated math from the help file. I appreciate your patience. That is awesome: the unique variance explained after removing the variance explained by every other region. Wow. That decreases the limitation that the correlation between region A and B is not direct and is caused by a third region C. I will need to think about that a ton and put it into an entirely separate publication.
For now, because I will use the FZ matrix in the fetal fat_lme_prep.py program, my PC matrix zeros are only a concern in case I made a mistake somewhere. Thank you again for your help and patience. I checked all 77 runs, and I get the same result. Would you be willing to look at a run? If yes, is there somewhere that I could copy the data on Biowulf? On the other hand, maybe I should run some diagnostics on my own. Does anything come to mind? For example, should I try demeaning the data first?
Sincerely,
Dante