[R] lm with an arbitrary number of terms

[John Fox]

Dear Richard,

At 05:49 PM 4/2/2003 +0100, Richard Nixon wrote:

>Any ideas how to do this?
>
>data.frame is a data frame with column names "x1",...,"xn"
>y is a response variable of length dim(data.frame)[1]
>
>I want to write a function
>
>function(y, data.frame){
>     lm(y~x1+...+xn)
>}
>
>This would be easy if n was always the same.
>If n is arbitrary how could I feed the x1+...+xn terms into 
>lm(response~terms)?

If y contains the *name* of the response variable, which is also in the 
data frame, then the following should work:

fun <- function(y, df){
     lm(as.formula(paste(y, "~.")), data=df)
     }

Alternatively, if y is a vector and is not in the data frame, then you 
might try

fun <- function(y, df){
     df <- data.frame(y, df)
     lm(y~., data=df)
     }

I hope that this helps,
  John
____________________________
John Fox
Department of Sociology
McMaster University
email: jfox at mcmaster.ca
web: http://www.socsci.mcmaster.ca/jfox