[R] avoiding "multiple actual arguments" in default function behavior

[William Dunlap]

> Suppose I'm creating a function that sets default ylab and xlab behaviors:
> 
> plotx = function(x, y, ...){
>     plot(x,y, ylab="", xlab="",...)
> }
> 
> The problem is, on occasion, I actually want to override the defaults
> in my function.

Make xlab and ylab arguments to your function.
  plotx2 <- function(x, y, ..., xlab="", ylab="") {
    plot(x, y, xlab=xlab, ylab=ylab, ...)
  }
(I put them after the ... in the argument list so they must be fully
named in the call.)

Bill Dunlap
TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Dustin Fife
> Sent: Wednesday, February 05, 2014 8:11 AM
> To: r-help
> Subject: [R] avoiding "multiple actual arguments" in default function behavior
> 
> Suppose I'm creating a function that sets default ylab and xlab behaviors:
> 
> plotx = function(x, y, ...){
>     plot(x,y, ylab="", xlab="",...)
> }
> 
> The problem is, on occasion, I actually want to override the defaults
> in my function. I would like to do the following:
> 
> plotx(1:100, 1:100, xlab="I Don't Work!")
> 
> 
> But I get the "multiple actual arguments" error message (which makes
> sense). Does anyone know how to set a default (like plotx does), but
> allow it to change if the user specifies the same argument via ...?
> 
> I tried doing something like this:
> 
> plotx = function(x, y, ...){
>     args = list(...)
>     yl = ifelse(!is.null(args$ylab), args$ylab, "")
>     xl = ifelse(!is.null(args$xlab), args$xlab, "")
>     plot(x,y, ylab=yl, xlab=xl,...)
> }
> 
> but got the same error. I then started thinking that maybe I can
> remove the ylab and xlab arguments from ..., but I don't know how I'd
> do that. Any ideas of how to remove it? Or, is there a better way of
> doing this? Thanks!
> 
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