[R] extracting estimated covariance parameters from lme fit

Dear all Apologies in advance as this seems like a trivial question. Nonetheless, a question I haven't been able to resolve myself !. Within a single repetition of a simulation (to be repeated many times) I am fitting the following linear mixed model using lme... Y_{gtr} = \mu + U_{g} + W_{gt} +

[R] lme model specification

Dear all this is a question of model specification in lme which I'd for which I'd greatly appreciate some guidance. Suppose I have data in long format gene treatment rep Y 11 1 4.32 11 2 4.67 11 3 5.09 .. .. .. .. .