Dear CONN users,

I'm interested in running a PPI analysis in CONN. My dataset consists of 15 subjects, each one with 10 functional sessions. There are three "tasks": NF, FB, and Bas, the latter being the baseline. Here, I want to analyze the linear trend for NF blocks over time (i.e. sessions, or 10 time-points).

So, I found in the forum (https://www.nitrc.org/forum/message.php?...) the suggestion of using kron(eye(15),null([-4.5 -3.5 -2.5 -1.5 -.5 .5 1.5 2.5 3.5 4.5])') as a second-level covariate. Here I am already adapting the covariate for 15 subjects and 10 sessions. I assume that this step should be in Setup --> Covariates (2nd-level) (?)

My first question is why not to use simply [-4.5 -3.5 -2.5 -1.5 -.5 .5 1.5 2.5 3.5 4.5] in Results (2nd-level) specifying the 10 conditions (in this case sessions)?

Second question: in Setup --> Covariates (2nd-level), I create the new covariate WithinSubject and try to use kron(eye(15),null([-4.5 -3.5 -2.5 -1.5 -.5 .5 1.5 2.5 3.5 4.5])') as values, but then I receive the message: Incorrect input string size (expected array size = [1x15]; entered array size = [135x150]). I guess I misunderstood what it should be done or CONN changed the way one specifies 2nd-level covariates since the time of the recommendation mentioned above? 

Third question: as recommended in https://www.nitrc.org/forum/message.php?... I'm defining only NF and FB blocks and leaving Bas as the implicit baseline. However, as I'm interested only in NF blocks, how to analyze the effect only in NF? Would it change the way I define the 2nd-level covariate?

Thank you very much in advance!
Gustavo Pamplona