[R] automatic model specification

[Andrej Kveder]

Dear listers,


I must first say that all the suggestions and help I
got from the list so far was of great help to my work.

I approach you with another question. Is it possible
to generate an automatic specification of the formula
for lme (or other models in R)? Let me clarify. I'm
using models in a simulation run and can have variable
number of variables in the data. I would like to
generate the formula as a string automaticaly
depending on the data structure. I had something like
this in mind:

my.formula<-"y~x1+x2+x3"
my.ran<-"~ x1"
d<-groupedData(my.formula | inter, data=d.n.data)
model<-lme(my.formula, data=d, random=my.ran | group)

I know this doesn't work. The error reports wrong type
for the formula. Is there a way to do this? 

Thanks for all the help and suggestions

Andrej

_________
Andrej Kveder, M.A.
researcher
Institute of Medical Sciences SRS SASA; Novi trg 2,
SI-1000 Ljubljana, Slovenia
phone: +386 1 47 06 440   fax: +386 1 42 61 493