[R] how do I define a function which is equivalent to `deparse(substitute(x))`?
David Winsemius
dwinsemius at comcast.net
Mon Dec 12 23:54:14 CET 2016
> On Dec 12, 2016, at 2:07 PM, Fox, John <jfox at mcmaster.ca> wrote:
>
> Dear Frederick,
>
> I found this a challenging puzzle, and it took me awhile to come up with an alternative, and I think slightly simpler, solution:
>
>> desub <- function(y) {
> + deparse(eval(substitute(substitute(y)),
> + env=parent.frame()))
> + }
>
>> f <- function(x){
> + message(desub(x))
> + }
>
>> f(log)
> log
Exactly the same answer as the crossposting elicited:
http://stackoverflow.com/questions/41083293/in-r-how-do-i-define-a-function-which-is-equivalent-to-deparsesubstitutex
--
David
>
> Best,
> John
>
> -----------------------------
> John Fox, Professor
> McMaster University
> Hamilton, Ontario
> Canada L8S 4M4
> Web: socserv.mcmaster.ca/jfox
>
>
>
>
>> -----Original Message-----
>> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
>> frederik at ofb.net
>> Sent: December 11, 2016 8:35 PM
>> To: r-help at r-project.org
>> Subject: Re: [R] how do I define a function which is equivalent to
>> `deparse(substitute(x))`?
>>
>> Dear R-Help,
>>
>> I was going to ask Jeff to read the entire works of William Shakespeare to learn
>> why his reply was not helpful to me...
>>
>> Then I realized that the answer, as always, lies within...
>>
>> desub <- function(y) {
>> e1=substitute(y, environment())
>> e2=do.call(substitute,list(e1), env=parent.frame())
>> deparse(e2)
>> }
>>
>> Sorry to trouble the list; other solutions still welcome.
>>
>> Cheers,
>>
>> Frederick
>>
>> On Sun, Dec 11, 2016 at 12:46:23AM -0800, Jeff Newmiller wrote:
>>> No. Read Hadley Wickham's "Advanced R" to learn why not.
>>> --
>>> Sent from my phone. Please excuse my brevity.
>>>
>>> On December 10, 2016 10:24:49 PM PST, frederik at ofb.net wrote:
>>>> Dear R-Help,
>>>>
>>>> I asked this question on StackOverflow,
>>>>
>>>> http://stackoverflow.com/questions/41083293/in-r-how-do-i-define-a-fu
>>>> nction-which-is-equivalent-to-deparsesubstitutex
>>>>
>>>> but thought perhaps R-help would be more appropriate.
>>>>
>>>> I want to write a function in R which grabs the name of a variable
>>>> from the context of its caller's caller. I think the problem I have
>>>> is best understood by asking how to compose `deparse` and `substitute`.
>>>> You can see that a naive composition does not work:
>>>>
>>>> # a compose operator
>>>>> `%c%` = function(x,y)function(...)x(y(...))
>>>>
>>>> # a naive attempt to combine deparse and substitute
>>>>> desub = deparse %c% substitute
>>>>> f=function(foo) { message(desub(foo)) }
>>>>> f(log)
>>>> foo
>>>>
>>>> # this is how it is supposed to work
>>>>> g=function(foo) { message(deparse(substitute(foo))) }
>>>>> g(log)
>>>> log
>>>>
>>>> Is there a way I can define a function `desub` so that `desub(x)` has
>>>> the same value as `deparse(substitute(x))` in every context?
>>>>
>>>> Thank you,
>>>>
>>>> Frederick Eaton
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>> 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 -- To UNSUBSCRIBE and more, see
>> 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 -- To UNSUBSCRIBE and more, see
> 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.
David Winsemius
Alameda, CA, USA
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