We are working in Matlab to analyze longitudinal data using the mass-univariate approach to Linear Mixed Effects (LME) Modeling.

Step 1: Below is the design matrix (first few rows) we created in an effort to compare subjects with low, moderate, and high drinking behavior with respect to time (3 groups).

1 0 1 0 0 0 0 0

1 3.0 1 3.0 0 0 0 0

1 0 1 0 0 0 0 0

1 1.2 0 0 1 1.2 0 0

1 2.3 0 0 0 0 1 2.3

1 3.5 0 0 0 0 1 3.5

1 0 1 0 0 0 0 0

Column 1 - intercept ones; 2 - time (years since baseline scan); 3 - low drinking group; 4 - low drinking x time; 5 - mod drinking group; 6 - mod drinking x time; 7 - high drinking group; 8 - high drinking x time

Step 2: To compare low/moderate drinking, mod/high drinking, and low/high drinking, we created the contrast matrix below:

CM=[0 0 0 1 0 -1 0 0; 0 0 0 0 0 1 0 -1; 0 0 0 1 0 0 0 -1]

Row 1 - low/mod drinking; Row 2 - mod/high drinking; Row 3 - low/high drinking

Please let us know if the contrast matrix is appropriate for our design matrix and the comparisons we would like to make. This seems incorrect since there is only one output from "lme_mass_F(lhstats,CM);"

Thank you for your help.