[R] how to generate argument from a vector automatically

Adaikalavan Ramasamy ramasamy at cancer.org.uk
Tue Jul 12 12:52:37 CEST 2005

You can do it by subsetting the dataframe 

  df <- data.frame( y=rbinom(100, 1, prob=0.5), 
                    x1=rnorm(100), x2=rnorm(100), x3=rnorm(100),
                    z1=rnorm(100), z2=rnorm(100) )
  names <- c("x1", "x2", "x3")
  tree( y ~ . , data = df[ , c("y", names) ] )

This solution is useless when you want to consider interactions between
some terms etc. Another more flexible solution is from last example from
help(formula) :

   xnam <- paste("x", 1:3, sep="")
   call <- as.formula(paste("y ~ ", paste(xnam, collapse= "+")))
   tree( call, df )

Regards, Adai

On Tue, 2005-07-12 at 09:53 +0000, 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.
> could anybody give me a hint?
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