Dear SPMers,
My design matrix looks as following
columns 1-3: main effect F1
columns 4-5: main effect F2
columns 6-7: main effect F3
columns 8-13: interaction F1 F2
columns 14-19: interaction F1 F3
columns 20-23: interaction F2 F3
I thought I could get the main effect of F1 with:
[1 -1 0;
0 1 -1]
but SPM says it's invalid, what is it that I'm missing?
Thank you in advance,
AJ
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