[R] How to convert a list to a ... argument for a function

[Charles C. Berry]

On Tue, 5 Oct 2010, Richard R. Liu wrote:

> Hi,
>
>
> I have a function f <- function(..., func){ something }, where func is a
> function of the form function(...). Â I would like to pass func all the arguments
> passed to f except the last. Â I know that I can manipulate the variable number
> of arguments passed to f by converting ... to a list, i.e., arglist <-
> list(...). Â But how do I pass func the first n-1 list items of arglist (n <-
> length(arglist)), as n-1 arguments, not as one list of n-1 items?
>

One way:

foo <- function(...,func){
 	mc <- match.call()
 	mc[[1]] <-mc$func
 	mc$func <- NULL
 	mc[[ length(mc) ]] <- NULL
 	eval(mc) }

foo(1,2,3,4,func=c)
foo(1,2,4,3,func=sum)


or perhaps you meant like this:

foo <- function(...,func){
         mc <- match.call()
         mc[[1]] <-mc$func
         mc$func <- NULL
         eval(mc) }

foo(1,2,3,4,func=c)
foo(1,2,4,3,func=sum)


HTH,

Chuck

>
> Regards,
> Richard
>
>
>
> Richard R. Liu
> richard.liu at pueo-owl.ch
>
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>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901