I have resting state data for a large group of subjects investigated 1, 2, or 3 times.
I would like to model how a variable # impacts rsFC.

If I enter the following for 50 subjects

Session1 Session 2 Session3

SubjectA Scan_1 Scan_2
SubjectB Scan_1
SubjectC Scan_1 Scan_2 Scan_3
...
SubjectY Scan_1 Scan_2 Scan_3
SubjectZ Scan_1



Can I then enter the measure  # at each scan somehow as a 3X50 matrix such as
#1 #2 #3
SubjectA 25 35 15
SubjectB 33 na na
SubjectC 44 11 29
...
SubjectY 34 11 4
SubjectZ 22 na na

where #1, #2 and #3 is my measure at the three time points


My end goal is to see how # may impacts rsFC

What should my contrast variable look like?
 Scan_1, Scan_2, Scan_3, #1, #2, #3
0 0 0 1 1 1

will this give me the variance between scan sessions that is explained by variance in #, whole accounting for both the within subject and between subject design?
and how do I handle the cases with only one scan?

thanks

Clas