About a month ago I had a similar issue related to 'formula': http://tolstoy.newcastle.edu.au/R/e2/devel/07/05/3329.html
In summary: In S-Plus, the help for formula.data.frame says: This is a method for the function formula() for objects inheriting from class data.frame. If object is a model frame, the formula for the model frame is returned, otherwise a formula is deduced from the names of object. The first name is taken to be the response, and all the remaining names are pasted together additively. In R, the help for formula.data.frame is aliased to the help for formula, but does not clearly document the usage with data.frames. Kevin On 7/16/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote: > The formula attribute of the builtin CO2 dataset seems a bit strange: > > > formula(CO2) > Plant ~ Type + Treatment + conc + uptake > > What is one supposed to do with that? Certainly its not suitable for > input to lm and none of the examples in ?CO2 use the above. > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
