[R] Fortune?, was Re: Recovering object names when using the ... argument in a fn XXXX

[Achim Zeileis]

On Sat, 19 Oct 2013, Michael Dewey wrote:

> At 19:05 18/10/2013, William Dunlap wrote:
>> > However, I do not understand the
>> >    substitute(...())
>> > idiom. Would you care to explain it? (No is an acceptable  answer!).
>> 
>> I don't completely understand it either, I treat it as an idiom.  I saw it 
>> on this list once.
>> 
>> Bill Dunlap
>> Spotfire, TIBCO Software
>> wdunlap tibco.com
>
> Well it brightened up my day. Not sure whether that is sufficient or 
> necessary for it to be a fortune.

It made me smile as well so I've added it to the package on R-Forge now 
:-)

Best,
Z

>
>
>> > -----Original Message-----
>> > From: Bert Gunter [mailto:gunter.berton at gene.com]
>> > Sent: Friday, October 18, 2013 10:54 AM
>> > To: William Dunlap
>> > Cc: Dan Abner; r-help at r-project.org
>> > Subject: Re: [R] Recovering object names when using the ... argument in a 
>> fn XXXX
>> >
>> > Yes, similar, but better, as match.call() will get unwanted named
>> > arguments, too.
>> >
>> > However, I do not understand the
>> >
>> > substitute(...())
>> >
>> > idiom. Would you care to explain it? (No is an acceptable  answer!).
>> >
>> > I would have expressed it as:
>> >
>> > as.list(substitute(list(...)))[-1]
>> >
>> > to convert the parse tree to a list. (which is again better than using
>> > match.call() ).
>> >
>> > Best,
>> > Bert
>> >
>> > On Fri, Oct 18, 2013 at 10:27 AM, William Dunlap <wdunlap at tibco.com> 
>> wrote:
>> > >> I am using the ... argument to parmeterize a user define fn to accept
>> > >> multiple input objects. I subsquently save all these data as a list.
>> > >> Question: what is the best way to recover or extract the original 
>> object
>> > >> names that were fed to the fn?
>> > >
>> > > The following function, ellipsisInfo, returns character strings 
>> representing the
>> > > actual arguments to the function.  If the function was called with tags 
>> on the
>> > > arguments, as in ellipsisInfo(tag=argument), it makes those tags the 
>> names
>> > > on the returned character  vector.  It does not evaluate the ... 
>> arguments, so
>> > > you don't run into problems with evaluating arguments too soon or 
>> evaluating
>> > > ones that should not be evaluated most of the time.
>> > >
>> > > ellipsisInfo <- function(...) {
>> > >     # get the unevaluated expressions given as arguments
>> > >     unevaluatedArgs <- substitute(...())
>> > >     # convert those expressions to text (truncate to single line)
>> > >     unevaluatedArgsAsText <- vapply(unevaluatedArgs, 
>> function(a)deparse(a)[1], "")
>> > >     unevaluatedArgsAsText
>> > > }
>> > >
>> > > E.g.,
>> > >
>> > >> i <- ellipsisInfo(x, log(10), e=exp(1), onProblem=stop("there was a 
>> problem"))
>> > >> i
>> > >
>> > >                             "x"
>> > >
>> > >                       "log(10)"
>> > >                               e
>> > >                        "exp(1)"
>> > >                       onProblem
>> > > "stop(\"there was a problem\")"
>> > >> ifelse(names(i)=="", i, names(i)) # use tag if supplied, otherwise 
>> argument itself
>> > > [1] "x"         "log(10)"   "e"
>> > > [4] "onProblem"
>> > >
>> > > Bill Dunlap
>> > > Spotfire, 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 Dan Abner
>> > >> Sent: Friday, October 18, 2013 9:06 AM
>> > >> To: r-help at r-project.org
>> > >> Subject: [R] Recovering object names when using the ... argument in a 
>> fn XXXX
>> > >>
>> > >> Hi all,
>> > >>
>> > >> I am using the ... argument to parmeterize a user define fn to accept
>> > >> multiple input objects. I subsquently save all these data as a list.
>> > >> Question: what is the best way to recover or extract the original 
>> object
>> > >> names that were fed to the fn?
>> > >>
>> > >> Thanks,
>> > >>
>> > >> Dan
>> > >>
>> > >>       [[alternative HTML version deleted]]
>> > >>
>> > >> ______________________________________________
>> > >> 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.
>> > >
>> > > ______________________________________________
>> > > 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.
>> >
>> >
>> >
>> > --
>> >
>> > Bert Gunter
>> > Genentech Nonclinical Biostatistics
>> >
>> > (650) 467-7374
>
> Michael Dewey
> info at aghmed.fsnet.co.uk
> http://www.aghmed.fsnet.co.uk/home.html
>
> ______________________________________________
> 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.
>