Stata-using friends, I have some troubles in handling the accomplishment of Cross Classified Random Coefficient Model using Stata.I have two cross classified variables, cohort and period variable in unnested level two and level three. I have found the stata command， "xtmixed weight week || _all: R.id || _all: R.week"， but it serves to do random intercept model. however, i want to do random coefficient model, it seems not to provide a stata command. Who could help me realize it ? thanks.