Correlation

To whom it may concern, 


I have two questions;

First, how do I find/calculate an "R-value"/correlation value between ROIs? And how do I choose each ROIs to have that specific r-values?

Second, I wich to open thees correlation values in mricron, but get this message "Errorin Reading NIFTI header.0". is there a problem with my results?

Thank you in advance, 
Hanna