[R] how to generate argument from a vector automatically

Uwe Ligges ligges at statistik.uni-dortmund.de
Tue Jul 12 12:49:33 CEST 2005

zhihua li wrote:

> hi netters
> i have a vector NAMES containing a series of variable names: 
> NAMES=c(x,r,z,m,st,qr,.....nn).
> i wanna fit a regression tree by using the code:            
> my.tree<-tree(y~x+r+z+m+....nn,my.dataframe)
> but i don't want to type out "x+r+z+m+....+nn" one by one, as there are 
> so many variables. besides, sometimes i wanna put the code in a 
> function. so i need to have the argument "x+r+z+m+....+nn" generated 
> from NAMES automatically.
> i've tried the code: paste(X,collpase="+") but it didn't work.

You have to construct it as.formula() from these characters,
or even better use short term formulas such as "y~.", if all variables
should be used anyway.

Uwe Ligges

> could anybody give me a hint?
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