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 <wdun...@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-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
>> Behalf
>> Of Dan Abner
>> Sent: Friday, October 18, 2013 9:06 AM
>> To: r-help@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@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@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
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
