[R] How to output name of object

[Bert Gunter]

Would

f <- function (...)
{
  sapply(substitute(list(...)),deparse)[-1]
}

> f(a1=log(1:4), m1=1:4, c1=pi)
        a1         m1         c1
"log(1:4)"      "1:4"       "pi"

be equivalent?
I find the substitute(...()) construction completely mysterious, while
substitute(list(...)) makes sense to me.

Cheers,
Bert




Bert Gunter
Genentech Nonclinical Biostatistics
(650) 467-7374

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
Clifford Stoll




On Wed, Jun 18, 2014 at 5:41 AM, Prof Brian Ripley
<ripley at stats.ox.ac.uk> wrote:
> On 18/06/2014 12:54, Jim Lemon wrote:
>>
>> On Wed, 18 Jun 2014 04:24:58 PM yzh lin wrote:
>>>
>>> Hi, every R user,
>>>
>>>     I wanna output  names of objects, I googled codes from website,
>>
>> but it
>>>
>>> was not what I wanted.
>>>
>>> the codes are as following:
>>>
>>> f <- function (...)
>>> {
>>>    unevaluatedArgs <- substitute(...())
>>>    evaluatedArgs <- list(...)
>>>    stopifnot(length(unevaluatedArgs) == length(evaluatedArgs))
>>>    tags <- vapply(unevaluatedArgs, FUN=function(x) deparse(x)[1],
>>>                   FUN.VALUE=character(1))
>>>    if (!is.null(tmp <- names(evaluatedArgs))) {
>>>      # if argument is tagged, tag=expr, use the tag
>>>      i <- !is.na(tmp) & tmp != ""
>>>      tags[i] <- tmp[i]
>>>    }
>>>    tags
>>> }
>>>
>>> f(a1=log(1:4), m1=1:4, c1=pi)
>>>
>>> results:
>>>>
>>>> f(a1=log(1:4), m1=1:4, c1=pi)
>>>
>>>
>>>    a1   m1   c1
>>> "a1" "m1" "c1"
>>>
>>>
>>> what I wanted is outputting "log(1:4) " "1:4", "pi" , while not "a1" "m1"
>>> "c1" .
>>>
>>> Coulde someone tell me how to get the results I wanted?
>>>
>> Hi Yuanzhen,
>> This may be of some help:
>>
>> f<-function (...) {
>>    unevaluatedArgs <- unlist(substitute(...()))
>>    tags<-NA
>>    for(arg in 1:length(unevaluatedArgs))
>>     tags[arg]<-deparse(unevaluatedArgs[[arg]])
>>    tags
>> }
>>
>> f(a1=log(1:4), m1=1:4, c1=pi)
>> [1] "log(1:4)" "1:4"      "pi"
>
>
> Or simply
>
> f <- function(...) sapply(subsitute(...()), deparse)
>
> which even keeps the names.
>
> --
> 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
>
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