I wonder, why do not need to specify the structure of the variance covariance matrix and the lmer function library lme4, since using the lm function library nlme this is possible. Thank you.

  • $\begingroup$ Is your question about specifying/imposing a specific variance-covariance structure in lme4 (as opposed to nlme)? Did you read this related thread? $\endgroup$ – chl Apr 22 '15 at 13:38
  • $\begingroup$ My question is for what reason does not specify to individual intra covariance structure in lme4. $\endgroup$ – Matheus Henrique Dal Molin Rib Apr 22 '15 at 13:41
  • $\begingroup$ I think this thread (and many more via Google) addresses your question, then. $\endgroup$ – chl Apr 22 '15 at 13:44