Hello, I am trying to model blood pressure growth trajectories across two distinct periods (reactivity and recovery from a stressor). I am looking to examine rates of linear growth for levels of bp for each person within each period. I also include person-level predictors. I am currently modeling blood pressure as a function of each time point. However, there are 8 time points (4 during the reactivity phase and 4 during the recovery phase), and I would like to divide time into two periods, before minute 4 and after minute 4. Here is my SAS code modeling each time point (I use SAS 9.4): proc mixed data=third;
class condition time;
model systolic = time|condition;
repeated time / sub=id type=un;
lsmeans time|condition;
run; How can I create a spline model where I can get two separate coefficients (one before time=4 and one after time=4)? Thank you!
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