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

[b88207001 at ntu.edu.tw]

Hello dear uesRs,

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  
if nlme is unable to do it.

Many thanks in advance!

Best,
Yen