[R] Messing with the "..." argument

[Steve Lianoglou]

Hi all,

Sorry if this is documented somewhere, but trying to search and google for 
ways to alter my "..." argument is having me chasing my tail.

Is there someway that I can manipulate the elements in "..."? 
Specifically I'd like to use certain vars in "...", then remove them 
from "..." and pass the rest of "..." to another function.

Here's a short example: I'm adding more functionality to a generic 
method by defining how it works on a new class "MyClass":

setMethod('existingFunction', 'MyClass', function (object, ...) {
  vars <- list(...)
  doSomethingWith(vars$myCustomVar)
  
  # now I want to pass the rest of the vars down to another function,
  # let's say some plotting function, so I'd like to remove
  # `myCustomVar` from "...", keep the rest of the vars and just
  # pass the valid "..." elements down through the call chain
  
  doSomePlot(somethingSane, ...)
})

Currently the `doSomePlot` that's called does fine until it passes the
rest of it's vars to the "real" plot method, at which point I'll get
a warning like:

Warning messages:
1: In plot.window(...) : "myCustomVar" is not a graphical parameter
2: In plot.xy(xy, type, ...) : "myCustomVar" is not a graphical parameter
3: In axis(side = side, at = at, labels = labels, ...) :
  "myCustomVar" is not a graphical parameter
4: In axis(side = side, at = at, labels = labels, ...) :
  "myCustomVar" is not a graphical parameter
5: In box(...) : "myCustomVar" is not a graphical parameter
6: In title(...) : "myCustomVar" is not a graphical parameter

Depending on what the name of myCustomVar is, this can work even with
the warnings, which is passable. It might also bail if myCustomVar
happens to share a name with a real plotting var, but has an illegal
value for it.

Anyway, while there are ways it can work in this case, I'm just wondering
if I can remove elements from "..." and side-step these warning/error issues
altogether.

Since "vars <- list(...)" works to create a list of arguments from "...",
I'm guessing there must be a way to take an already existing list variable
and turn its name/value pairs into an appropriate "..." object?

Thanks for any help,
-steve