R help - Oct 2013 - 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]]

I'm not exactly sure what you mean by "names." Does the following
meet
your needs?

f <- function(...)names(list(...))
> f(a=2,b=3)
[1] "a" "b"
> f(a=2,3)
[1] "a" ""

If not, a reproducible example of what you want might be helpful.

Cheers,
Bert




On Fri, Oct 18, 2013 at 9:05 AM, Dan Abner <dan.abner99 at gmail.com>
wrote:
> 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.


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

(650) 467-7374

1. Always cc to the list unless it is truly a private offlist reply.
This is to get help from a wider audience, as may well be required
here. Translation: Take my "solution" with a grain of salt. It is
fragile at best.

2. I think ?match.call and ?deparse are what you're looking for:

f <- function(...){
  deparse(match.call())
}
> g(a,b,sqrt(c(1,2,5)))
[1] "a"                "b"                "sqrt(c(1, 2,
5))"

Cheers,
Bert




On Fri, Oct 18, 2013 at 9:36 AM, Dan Abner <dan.abner99 at gmail.com>
wrote:
> Hi Bert,
>
> Thanks for your response. Please see example below:
>
>
> d1<-data.frame(x1=runif(100),x2=runif(100))
> d2<-data.frame(x3=runif(100),x4=runif(100))
> d3<-data.frame(x5=runif(100),x6=runif(100))
> set1 <- function(...,by){
>     df.name <<- list(...)
>     name1<<-names(list(...))
> }
>
> set1(d1,d2,d3)
>
> I need to be able to recover whatever input data frame names that the user
> passes to set1() (preferably in the character vector).
>
>> name1
> NULL
>
> Here is another possible call to the fn:
>
> set1(d1,d2)
>
>
>
>
>
>
> On Fri, Oct 18, 2013 at 12:26 PM, Bert Gunter <gunter.berton at
gene.com>
> wrote:
>>
>> I'm not exactly sure what you mean by "names." Does the
following meet
>> your needs?
>>
>> f <- function(...)names(list(...))
>>
>> > f(a=2,b=3)
>> [1] "a" "b"
>> > f(a=2,3)
>> [1] "a" ""
>>
>> If not, a reproducible example of what you want might be helpful.
>>
>> Cheers,
>> Bert
>>
>>
>>
>>
>> On Fri, Oct 18, 2013 at 9:05 AM, Dan Abner <dan.abner99 at
gmail.com> wrote:
>> > 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.
>>
>>
>>
>> --
>>
>> Bert Gunter
>> Genentech Nonclinical Biostatistics
>>
>> (650) 467-7374
>
>


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

(650) 467-7374

> 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.