On 16-Jul-07 13:57:56, Ted Harding wrote: > On 16-Jul-07 13:28:50, Gabor Grothendieck 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. > > I think one is supposed to ignore it! (Or maybe be inspired to > write a mail to the list ... ). > > I couldn't find anything that looked like the above formula from > str(CO2). But I did spot that the order of terms in the formula: > Plant, Type, treatment, conc, uptake, is the same as the order > of the "columns" in the dataframe. > > So I tried: > > D<-data.frame(x=(1:10),y=(1:10)) > > formula(D) > x ~ y > > So, lo and behold, D has a formula! > > Or does it? Maybe if you give formula() a dataframe, it simply > constructs one from the "columns".
Now that I think about it, I can see a use for this phenomenon: > formula(CO2) Plant ~ Type + Treatment + conc + uptake > formula(CO2[,2:5]) Type ~ Treatment + conc + uptake > formula(CO2[,3:5]) Treatment ~ conc + uptake > formula(CO2[,4:5]) conc ~ uptake > formula(CO2[,c(5,1,2,3,4)]) uptake ~ Plant + Type + Treatment + conc Could save a lot of typing! Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 094 0861 Date: 16-Jul-07 Time: 15:14:38 ------------------------------ XFMail ------------------------------ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
