I fit a complicated model in proc glimmix with 2 categorical variables (6 and 8 levels respectively) and the linear and quadratic form of a continuous variable with all interactions.

The 3-way interaction is significant and I want to isolate the regression models for each combination of the two categorical variables and calculate the maxima (derivative of quadratic function for each combination).

My problem is that there are many levels of categorical variables and I find it difficult to correctly estimate all parameter estimates.

Is there a way to get the actual parameter estimates without having to manually calculate them? Or is there an example of something as complicated so I can learn how to do it?

Thanks