[R] How to make a function aware of its own call arguments

[sbihorel]

Thanks for the precision.

On 3/24/2016 10:40 AM, Duncan Murdoch wrote:
> On 24/03/2016 10:28 AM, sbihorel wrote:
>> Hi,
>>
>> Thanks for your suggestion.
>>
>> missing(x) works only if x is not altered within the function, which is
>> not the case in my actual function (which is more complex than the
>> example function I send in my previous post).
>
> That's not quite true:  missing(x) works *before* x is altered within 
> the function.  It works even if x has a default value.
>
> So your myf2 could just use missing(c):
>
> myf2 <- function(a=1, b=2, fun=NULL, c=myfun1(b,fun)){
>
>    if (myf1(b,fun)>0 && missing(c)){
>      c <- b
>    }
>    print(list(a,b,c))
> }
>
>
>>
>> Are you aware of any function what would query the original function
>> call arguments no matter what happens in the function?
>
> The match.call() function does that, but I think you don't need that:
>
> f <- function(x = 1, ...) {
>   x <- 2
>   match.call()
> }
> f(3)
> ## Prints:  f(x = 3)
>
> Duncan Murdoch
>
>>
>> Sebastien
>>
>> On 3/24/2016 8:47 AM, Jeff Newmiller wrote:
>> > Don't provide a default value for c in the parameter list. Then you
>> > can use the missing() function to make decisions, including whether to
>> > generate a default value for c or not.
>> > --
>> > Sent from my phone. Please excuse my brevity.
>> >
>> > On March 24, 2016 5:11:43 AM PDT, sbihorel
>> > <Sebastien.Bihorel at cognigencorp.com> wrote:
>> >
>> >     Hi,
>> >
>> >     Please consider the following functions:
>> >
>> >     myf1 <- function(x,fun){
>> >         if (is.null(fun)){
>> >           x
>> >         } else {
>> >           do.call(fun, list(x))
>> >         }
>> >     }
>> >
>> >     myf2 <- function(a=1, b=2, fun=NULL, c=myfun1(b,fun)){
>> >
>> >         if (myf1(b,fun)>0 & <c was not provided in function call>){
>> >           c <- b
>> >         }
>> >         print(list(a,b,c))
>> >     }
>> >
>> >     myf2(a=2,b=3,fun=exp)
>> >     myf2(a=2,b=3,fun=exp,c=4)
>> >
>> >     I need to replace "<c was not provided in function call>" by 
>> some code
>> >     that would make myf2 aware of it own calls and of the fact that 
>> the c
>> >     argument was provided or not in the function calls.
>> >
>> >     Thanks for your help
>> >
>> >     Sebastien
>> >
>> > 
>> ------------------------------------------------------------------------
>> >
>> >     R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> >     https://stat.ethz.ch/mailman/listinfo/r-help
>> >     PLEASE d
>> >       o read
>> >     the posting guidehttp://www.R-project.org/posting-guide.html
>> >     and provide commented, minimal, self-contained, reproducible code.
>> >
>> -- Sebastien Bihorel Associate Director, Pharmacometrics Buffalo Office:
>> +1-716-633-3463 ext. 323 | Website <http://www.cognigencorp.com>
>> <http://www.simulations-plus.com/Default.aspx>
>>
>> ______________________________________________
>> 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.
>

-- 
Sebastien Bihorel
Associate Director, Pharmacometrics
Buffalo Office: +1-716-633-3463 ext. 323 | Website 
<http://www.cognigencorp.com>
<http://www.simulations-plus.com/Default.aspx>