Hi, Sondos-
Then it sounds like you would want the information along the diagonal of a matrix.
For example, the number of tracts *between separate* targets (e.g., ROI 002 and 003) is stored in an *off-diagonal* element (e.g., the column with 002 and row with 003, or row with 002 and column with 003) of the NT="number of tracts" matrix.
The number of tracts going through a single target (e.g., ROI 004) *to aaaanywhere else* -- to another target or not -- is stored in the *diagonal* element (e.g., the column with 004 and row with 004) of the NT matrix.
-pt