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Dear Reader, Currently I am running a vertex analysis. Because my participants were scanned in three different centers I want to include scanlocation as a covariate in my design. When I am using FEAT I demean the covariates and add two EV's. The first has the demeaned scores for scanlocation 1 and 2 with scanlocation 3 defined as 0. The second has the demeaned scores of scanlocation 1 and 3 with scanlocation 2 defined as 0. However FIRST demeans on its own so if I assign a value of 0, this 0 will get demeaned and won't be a 0 anymore. So, basically my question is: How do I include a categorical variable as covariate in my vertex analysis design? Kind regards, Steven van der Werff