[R] matching last argument in function
Gabor Csardi
csardi at rmki.kfki.hu
Tue Feb 12 20:05:04 CET 2008
It should be possible i think. You just supply all the arguments via
'...' and then cut off the last one. I don't see why this wouldn't work,
but maybe i'm missing something.
Gabor
On Tue, Feb 12, 2008 at 12:58:25PM -0600, Erik Iverson wrote:
> Alistair -
>
> I don't believe this is possible. The only way formal arguments (like
> expr) can be matched after a '...' is with *exact* name matching. Why
> do you want to avoid explicitly naming the expr argument?
>
> If you always want the expr argument last, you might be able to just use
> ... as the sole argument to your function, and strip off the last
> element inside the function as 'expr', and use all but the last element
> as your list of options. This requires that expr always be given last
> though. Probably best just to explicitly name the expr argument.
>
> Erik Iverson
>
> Alistair Gee wrote:
> > I often want to temporarily modify the options() options, e.g.
> >
> > a <- seq(10000001, 10000001 + 10) # some wide object
> >
> > with.options <- function(..., expr) {
> > options0 <- options(...)
> > tryCatch(expr, finally=options(options0))
> > }
> >
> > Then I can use:
> >
> > with.options(width=160, expr = print(a))
> >
> > But I'd like to avoid explicitly naming the expr argument, as in:
> >
> > with.options(width=160, print(a))
> >
> > How can I do this with R's argument matching? (I prefer the expr as
> > the last argument since it could be a long code block. Also, I'd like
> > with.options to take multiple options.)
> >
> > TIA
> >
> > ______________________________________________
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> > https://stat.ethz.ch/mailman/listinfo/r-help
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> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> 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.
--
Csardi Gabor <csardi at rmki.kfki.hu> UNIL DGM
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