Dear Doug,
I'm performing a linear regression over one sample with a design matrix including columns for one continuous-valued predictor whose effect on neural measures I'm interested
in testing, several covariates to adjust for (continuous- or binary-valued such as age, sex, total intracranial volume, and other demographic groupings), and an intercept.
The contrast matrix I'll be testing will have 1 in the column corresponding to the column in the design matrix containing the predictor of interest and zeros in all other columns.
In addition, I was interested in performing the same linear regressions over subsets
of the group to determine whether the pattern associated with the predictor-of-interest is persistent. That's why I want to stack surfaces
for different sets of subjects (without recreating surfaces registered to fsaverage_sym for each subjects' laterality
indices for each instance). This way I could repeat the same contrast, except subsetting rows of the design matrix for subjects in the given sample.
Thank you.
Best,
Chintan