Set up DOE with symmetry
I want to set up a DOE with categorical variables. There are two variables (X1, X2) with the same categories (L1, L2, L3, ...) and the problem is L1L2 is the same as L2L1. That is if X1=L1 and X2=L2, then the experiment is same if X1=L2 and X2=L1. This is true for all other combinations too. How can I set up DOE that recognizes this? I tried using constraints, but I don't know how to add this. Tha...