在内存限制增加后，lme使Rstudio崩溃并且PC无响应

I am working with a data set of 205 observations and 2 explanatory variables : site (two levels) and strain ( 21 levels ). I am trying to fit a mixed model to the data when strain is the fixed variable. the experiment is not balanced ( i.e. the repetitions in each strainXsite cells are not equal ). And I use Rstudio 3.0.2; windows 8. I am working with a data set of 205 observation