Dear Dr. Allefeld,
I was trying to run the cvMANOVA on my dataset and I encountered an issue.
My task is a 2x2 factorial design (factors: category (2) and familiarity (2)), with 9 runs (sessions) in total.
For each session, I have the following regressors:
• 4 parametric regressors modelling each factorial combination of category and familiarity. For each of these 4 aggressors,
we also added a parametric modulator.
• 2 regressors modelling auditory cues and subject’s response
• 6 confound regressors modelling motion correction parameters.
In addition, in some participants we have an additional regressor modelling errors (or missed responses), that we inserted at the very end, so that it can be zero-padded by your function as reported in the readme.txt file.
The issue we are encountering is relative to setting up the contrasts for the cvMANOVA. We are interested for the moment in computing category and familiarity main effects, both for “regular” regressors and for their parametric counterpart, to understand where in the brain neural response is modulated by our parameter.
We set up the contrasts as follows:
%Main effect
Cs{1} = [1 0 -1 0 1 0 -1 0 0 0];
%Parametric main effect
Cs{2} = [0 1 0 -1 0 1 0 -1 0 0];
In the second contrast, we aim to replicate the first but this time using the parametric regressors factorXparameterXbf, as reported in SPM.
When we run the cvMANOVA, we encounter the following error:
Error using cvManovaCore (line 82)
contrast 2 is not estimable in session X!
This happens only with the parametric contrast, with the “regular” main effect the computation starts just fine. We tried on multiple subjects, the same error message appears and the session number that creates the error varies systematically.
Following another question we found in this thread (#27) and thinking the error might be due to the additional regressor present in some participants, we tried and run the cvMANOVA only in participants which did not commit any error (so with an equal number of regressors in each run), but the same error message appeared.
Here I attach an SPM.mat file of a participant without the additional error regressor (https://we.tl/t-F2tSL0yLdv).
Thanks for your help.
Best,
Flavio