R help - May 2007 - Scoped options setting?

Is there any way to set options during the evaluation of a particular
expression, with them automatically reset when control leaves that
expression, however that happens?  Kind of like "let" on a
"special"
variable does in Lisp.  I naively tried

with(options(warn=-1), {
    fit <- fitdistr(data, 'weibull')  # complains about NaNs
})

but this leaves options('warn') set to -1 afterward.  I can save and
restore the value explicitly, but then if fitdistr() throws an error,
it won't get reset...

zw

?on.exit

But here, you want suppressWarnings.

On Wed, 16 May 2007, Zack Weinberg wrote:
> Is there any way to set options during the evaluation of a particular
> expression, with them automatically reset when control leaves that
> expression, however that happens?  Kind of like "let" on a
"special"
> variable does in Lisp.  I naively tried
>
> with(options(warn=-1), {
>    fit <- fitdistr(data, 'weibull')  # complains about NaNs
> })
>
> but this leaves options('warn') set to -1 afterward.  I can save
and
> restore the value explicitly, but then if fitdistr() throws an error,
> it won't get reset...
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

On Wed, 16 May 2007, Zack Weinberg wrote:
> Is there any way to set options during the evaluation of a particular
> expression, with them automatically reset when control leaves that
> expression, however that happens?  Kind of like "let" on a
"special"
> variable does in Lisp.  I naively tried
>
You could write with_options() as

with_options <-function(optionlist, expr){
        oldoptions<-options(optionlist)
        on.exit(options(oldoptions))
        eval(substitute(expr), parent.frame())
}

and then do
   with_options(list(warn=-1),  whatever)

 	-thomas