R help - Jul 2005 - how to generate argument from a vector automatically

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?

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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> PLEASE do read the posting guide!
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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?
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html