try :
my_formula = as.formula(paste("y~",xxx))
lm(my_formula)

note that you can play with substr  in paste to change your formula
> paste("y~",substr(xxx,1,5))
[1] "y~ x1+x2"
> paste("y~",substr(xxx,4,8))
[1] "y~ x2+x3"

furthermore, with 10 predictors x1 x2 ...x10  for instence, you can
create 2 array of indice where to start and end the substr and do it in
a loop for multi fit...

best,

yves

> On 11/18/05, Juni Joshi <joshi_juni@hotmail.com> wrote:
> >
> >   I  need  to fit a number of models with different number of predictors
> >   in  each  model.  Say for example, I have three predictors: x1, x2, x3
> >   and I want to fit three models:
> >
> >   lm(y~x1+x2)
> >   lm(y~x2+x3)
> >   lm(y~x1+x2+x3)
> >
> >   Instead  of  typing  all  models,  what I want is to create a variable
> >   which  can  take  the right hand side of the models. I tried this with
> >   paste function.
> >
> >   xxx <- paste("x1","x2",sep=+) for the first
> >   xxx <- paste("x2","x3", sep = +) for the second
> >   xxx  <-  paste("x1","x2","x2",  sep  = +) for the third and then fit a
> >   single model
> >
> >   lm(y~xxx)
> >
> >   It did not work. Please suggest how to do it.
> >
> >   Thanks.
> >
> >   Jun
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
> >
> 
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
> 

	[[alternative HTML version deleted]]


