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 <[EMAIL PROTECTED]> 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
> > ______________________________________________
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> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
> >
>
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