[R] Use of the dot.dot.dot option in functions.

[Duncan Murdoch]

On 06/04/2011 12:04 PM, KENNETH R CABRERA wrote:
> Hi R users:
>
> I try this code, where "fun" is a parameter of a random generating
> function name, and I pretend to use "..." parameter to pass the parameters
> of different random generating functions.
>
> What am I doing wrong?
>
> f1<-function(nsim=20,n=10,fun=rnorm,...){
>      vp<-replicate(nsim,t.test(fun(n,...),fun(n,...))$p.value)
>      return(vp)
> }
>
> This works!
> f1()
> f1(n=20,mean=10)
>
> This two fails:
> f1(n=10,fun=rexp)
> f1(n=10,fun=rbeta,shape1=1,shape2=2)
>
> Thank you for your help.


I imagine it's a scoping problem: replicate() is probably not evaluating 
the ... in the context you think it is.  You could debug this by writing 
a function like

showArgs <- function(n, ...) {
   print(n)
   print(list(...))
}

and calling f1(n=10, fun=showArgs), but it might be easier just to avoid 
the problem:

f1 <- function(nsim=20,n=10,fun=rnorm,...){
     force(fun)
     force(n)
     localfun <- function() fun(n, ...)
     vp<-replicate(nsim,t.test(localfun(), localfun())$p.value)
     return(vp)
}