[R-sig-ME] complex residual variance

[Sven De Maeyer]

Hi all,

I'm not a frequent user of Lme4 and I have the habit to use mlwin for  
multilevel analyses. Nevertheless I'm willing to master lme4 further.

In my research I'm often faced with the situation where level 1  
variance (or residual variance in the mixed effects framework) isn't  
constant. E.g. I have longitudinal data on children, with multiple  
measurements (observations) of these children at a certain moment. As  
children get older these measurements seem to vary more and more. So  
the residual variance itself is a function of time. As a consequence  
there is heteroscedasticity.  Is there a possibility to explicitly  
model this in lme4? I know how to do it in mlwin, but is it possible  
in lmer?

With kind regards

Sven De Maeyer