Re: [R] using argument names (of indeterminate number) within a function

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Wed 20 Jul 2005 - 04:07:11 EST

On 7/19/05, Dirk Enzmann <dirk.enzmann@jura.uni-hamburg.de> wrote:
> Although I tried to find an answer in the manuals and archives, I cannot
> solve this (please excuse that my English and/or R programming skills
> are not good enough to state my problem more clearly):
>
> I want to write a function with an indeterminate (not pre-defined)
> number of arguments and think that I should use the "..." construct and
> the match.call() function. The goal is to write a function that (among
> other things) uses cbind() to combine a not pre-defined number of
> vectors specified in the function call. For example, if my vectors are
> x1, x2, x3, ... xn, within the function I want to use cbind(x1, x2) or
> cbind(x1, x3, x5) or ... depending on the vector names I use in the
> funcion call. Additionally, the function has other arguments.
>
> In the archives I found the following thread (followed by Marc Schwartz)
>
> http://finzi.psych.upenn.edu/R/Rhelp02a/archive/15186.html
> [R] returning argument names from Peter Dalgaard BSA on 2003-04-10 (stdin)
>
> that seems to contain the solution to my problem, but I am stuck because
> sapply(match.call()[-1], deparse) gives me a vector of strings and I
> don't know how to use the names in this vector in the cbind() function.
>
> Up to now my (clearly deficit) function looks like:
>
> test <- function(..., mvalid=1)
> {
> args = sapply(match.call()[-1], deparse)
> # and here, I don't know how the vector names in args
> # can be used in the cbind() function to follow:
> #
> # temp <- cbind( ???
> if (mvalid > 1)
> {
> # here it goes on
> }
> }
>
> Ultimately, I want that the function can be called like
> test(x1,x2,mvalid=1)
> or
> test(x1,x3,x5,mavlid=2)
> and that within the function
> cbind(x1,x2)
> or cbind(x1,x3,x5)
> will be used.
>

If you just need to pass them to cbind then just use cbind(...), e.g.

  test <- function(..., m) if (m > 1) cbind(...) else m

otherwise, use list(...) as shown by a previous answer or here

  test2 <- function(..., m) if (m > 1) length(list(...)) else m



R-help@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 Received on Wed Jul 20 04:13:11 2005

This archive was generated by hypermail 2.1.8 : Fri 03 Mar 2006 - 03:33:50 EST