[R] The three-dot question

[Feng Li]

Hi Michael,

Thanks for the reply.

On Mon, 2013-01-14 at 10:33 +0000, R. Michael Weylandt wrote: 
> Hi Feng,
> 
> I'm afraid I don't entirely understansd your question -- the `...`
> construct only allows you to pass variable numbers of arguments, not
> to have arbitrary access to the parent frames. You need to manually
> extract "b" from the dots inside of testFun.
> 
> Also, it's quite frowned upon to put ##rm(list = ls())## in your
> examples: it's the mailing list equivalent of asking a buddy to come
> over to help you move and then punching him in the face when he tries
> to lift your sofa.

The rm line just wants to declare there is no "b" in the global
environment. I did not mean people ought to try it. Also notice that
there is ">" in front of the rm. You won't get hurt if you just copy and
paste it. If it bites you, the mouse and keyboard did it:) 


Cheers,

Feng

> 
> Cheers,
> Michael
> 
> 
> On Mon, Jan 14, 2013 at 10:21 AM, Feng Li <m at feng.li> wrote:
> > Dear all,
> >
> > Why does not the three-dot accept arguments from the parent environment?
> > I am just confused with this error, can someone give me a hint?
> >
> >> rm(list=ls())
> >> testFun <- function(a, ...)
> > +   {
> > +     if(a){
> > +         print(a)
> > +       }else
> > +       {
> > +         print(b)
> > +       }
> > +   }
> >>
> >> myTask <- function(a)
> > +   {
> > +     b <- 3
> > +     testFun(a, b = b)
> > +   }
> >> myTask(FALSE)
> > Error in print(b) : object 'b' not found
> >
> >
> > Thanks in advance!
> >
> > Feng
> >
> > --
> > Feng Li
> > Department of Statistics
> > Stockholm University
> > SE-106 91 Stockholm, Sweden
> > http://feng.li/
> >
> > ______________________________________________
> > R-help at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.

-- 
Feng Li
Department of Statistics
Stockholm University
SE-106 91 Stockholm, Sweden
http://feng.li/