Dear FreeSurfer,

I have a longitudinal study (patients and controls) with two time points (i.e., baseline and six-weeks follow-up). I would like to use the LME model as it can handle unequal timing and different number of time points across subjects due to missing data. 

I would like to test if there is an effect of (a) time (b) group and (c) group x time interaction.

However, i am trouble with my design matrix X:

(1) How would i write X? 

Thanks in advance

Best regards

Kasper