[R] dots expansion

Liaw, Andy andy_liaw at merck.com
Tue Aug 3 13:58:24 CEST 2004

Duncan already gave the answer.  Here's a bit more detail:

rbindGroup <- function(...) {
    theList <- list(...)
    nGroup <- length(theList)
    size <- sapply(theList, nrow)
    result <- rbind(...)
    result <- cbind(result, rep(1:nGroup, each=size)

You probably want to add more error checks (like making sure all arrays have
the same number of columns).


> From: Viet Nguyen
> Hi list,
> I'm trying to write a function similar to rbind, except that needs to 
> add a factor to each component array before rbinding them together so 
> that the rows from different arrays are distinguishable.
> The problem that arose is how to loop through arguments in the dots 
> "..." list. I need to get a hand on each of them but don't 
> know how many 
> of them there are and what their names are.
> It'd be useful if I could look at how rbind(...) or c(...) do 
> this but 
> they are both Internal functions.
> Thanks in anticipation of help!
> Regards,
> viet
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