[R] having problems with the lme function

[8rino-Luca Pantani]

Hi Rodrigo,
it is not easy to anwer your question since you did not provide some
data to work with, nor what went wrong with your code.
Anyway, as far as I can catch I would try the following

library(nlme)
df.GD <- groupedData(Y ~ fact_A +fact_B|fact_C, data=DataFrame)
lme.1 <-lme(y~fact_A + fact_B, data=GD, random=~1|fact_C)

I'm not sure on the syntax for corClasses, but from the book cited below 
I see some examples like

corr=corAR1(0.8, form= ~1|fact_C)


Should you move definitely to R, I strongly suggest you to buy and study 
the following book

Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S
     and S-PLUS", Springer.

All the best


-- 
Ottorino-Luca Pantani, Università di Firenze
Dip. Scienza del Suolo e Nutrizione della Pianta
P.zle Cascine 28 50144 Firenze Italia
Tel 39 055 3288 202 (348 lab) Fax 39 055 333 273
OLPantani at unifi.it  http://www4.unifi.it/dssnp/