how to allow for factor-specific variance of random effect in lme

问题

I assume that the random effects variances in my mixed effect model will be different for different levels of the fixed factor BTyp.

Here is my model

fm2 <- lme(CA ~ 1 + pF+Tiefe+BTyp+Tiefe:pF+BTyp:pF, data=data2, 
           random = list(~ 1 + pF|Probe))
fm2_Btyphet<-update(fm2, weights=varIdent(form=~1|BTyp))

I managed to incorporate Btyp-specific variances for random effects using lmer function, but this function does not allow to consider variance heterogeneity of the within group error (which is better to consider in my case). My question is how to incorporate "Btyp"-specific variances for random effects using lme function?

Below you can see how it works with lmer function.

CA ~ 1 + pF + Tiefe + BTyp + Tiefe:pF + BTyp:pF + 
     (0 + Pind + pF | Probe) + (0 + Bind + pF | Probe) + (0 + Tind + pF | Probe) 


 Data: data2 

 AIC   BIC logLik deviance REMLdev

   21987 22092 -10975    21979   21951

Random effects:
 Groups   Name Variance Std.Dev. Corr 

 Probe    Pind 158.6058 12.5939         
          pF     2.4289  1.5585  -1.000 

 Probe    Bind 134.6383 11.6034         
          pF     2.7619  1.6619  -1.000 

 Probe    Tind 490.6714 22.1511         
          pF    46.3533  6.8083  -1.000 

 Residual      316.9860 17.8041    

Number of obs: 2530, groups: Probe, 45

Pind,Bind, Tind are indicator variables for different levels of BTyp.

来源：https://stackoverflow.com/questions/21409340/how-to-allow-for-factor-specific-variance-of-random-effect-in-lme