Greetings!!
I'm John, currently working on multilevel survival analysis using mestreg command.. I wanted to change the covariance structure through variance option but i'm getting an error stating that variable unstructured not available.
Please guide me how to create the covariance vartype and incorporate it in the model.

the code i used
mestreg age ib2.ASEX ib1.Intact_RGrain || Region:,variance(unstructured) distribution(lognormal)

Thanks in advance!!