[R-sig-ME] {nlme} Question about modeling Level two heteroscedasticity in HLM

[b88207001 at ntu.edu.tw]

Hello dear uesRs in mixed models,

I am working on modeling both level one and level two heteroscedasticity in
HLM. In my model, both error variance and variance of random intercept /
random slope are affected by some level two variables.

I found that nlme is able to model heteroscedasticity. I learned how to use
it for level one heteroscedasticity but don't know how to use it to model
the level two heteroscedasticity. I wonder if anyone could give me some
guide how to do it or any suggested software / packages (such as  
lme4?) if nlme is unable to do it.

Many thanks in advance!

Best,
Yen