[R] How to output name of object

[Prof Brian Ripley]

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)
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