[R] nlme questions

[Christian Mora]

Dear R users;

Ive got two questions concerning nlme library 3.1-65 (running on R 2.2.0 /
Win XP Pro). The first one is related to augPred function. Ive been working
with a nonlinear mixed model with no problems so far. However, when the
parameters of the model are specified in terms of some other covariates,
say treatment (i.e. phi1~trt1+trt2, etc) the augPred function give me the
following error: "Error in predict.nlme(object,
value[1:(nrow(value)/nL),,drop=FALSE], : Levels 0,1 not allowed for trt1,
trt2". The same model specification as well as the augPred function under
SPlus 2000 run without problems. The second question has to deal with the
time needed for the model to converge. It really takes a lot of time to fit
the model on R in relation to the time required to fit the same model on
SPlus. I can imagine this is related to the optimization algorithm or
something like that, but I would like to have a different opinion on these
two issues.

Thanks in advance

Christian Mora