[R] passing arguments via "..."

[Jonathan P Daily]

It is not clear to me exactly what you are looking to do, but if you are 
trying to check whether an argument has been passed via ..., I have used 
this convention before.

fun <- function(arg, ...) {
opts <- list(...)
if('opt' %in% names(opts)) # Do something...
}

Does that help?
--------------------------------------
Jonathan P. Daily
Technician - USGS Leetown Science Center
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Kearneysville WV, 25430
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"Is the room still a room when its empty? Does the room,
 the thing itself have purpose? Or do we, what's the word... imbue it."
     - Jubal Early, Firefly

r-help-bounces at r-project.org wrote on 03/29/2011 01:47:41 PM:

> [image removed] 
> 
> [R] passing arguments via "..."
> 
> Cable, Samuel B Civ USAF AFMC AFRL/RVBXI 
> 
> to:
> 
> r-help
> 
> 03/29/2011 01:51 PM
> 
> Sent by:
> 
> r-help-bounces at r-project.org
> 
> I would like to do something like the following:
> 
> Fancyhist<-function(x,...) {
> 
> # first, process x into xprocess somehow, then ...
> 
>   if (is.null(breaks)) {   # yes, I know this is wrong
> # define the histogram breaks somehow, then call hist:
>      hist(xprocess,breaks=breaks,...)
>   } else {
> # use breaks give in calling argument
>      hist(xprocess,...)
>   }
> 
> }
> 
> But, those of you who know R better than I do have already spotted that
> "is.null(breaks)" just won't work.  Neither does "exists" or "missing".
> 
> I can think of ways to do this involving new arguments with new names --
> like "histbreaks" or something -- but that seems inelegant.
> 
> Is there a way to do what I am trying to do here?
> 
> Thanks.
> 
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