[R] Arguments matching

[Stephane DRAY]

I just precise my problem (and correct the subject).

Is there a way to obtain a list where each element has the name of the 
argument (as interpreted by R). The problem with my approach is that if the 
user do not type the name of the argument, this element of the list 
(returned by as.list(as.call(appel1$callf))) has no name.
I suppose that a solution could be obtained using formals, match.args... 
but I did not find it.

Thanks





At 16:30 26/11/2004, Stephane DRAY wrote:
>Hello list,
>I have a question concerning argument matching I have read R Language 
>Definition before).
>I have a function multxby2 which takes as argument the call to another 
>function f1.
>I would like to take the values of xx from the call to f1 and use it in 
>multxby2.
>
>Here is an example:
>
>
>multxby2 <- function(callf) {
>     appel1<-match.call()
>     appel<-as.list(as.call(appel1$callf))
>
>     px<-pmatch(names(appel),"xx")
>
>     if(sum(is.na(px))!=length(appel)) print(appel[[which(!is.na(px))]]*2)
>     # else ...
>
>}
>
>f1=function(xx=2,y=3){}
>
>multxby2(f1(x=3))
>
>My problem is due to the various ways that a user can enter its arguments, 
>how to be sure to get xx from various call such as:
>
>multxby2(f1(3,2))
>multxby2(f1(y=2,3))
>
>Is there a way to do that avoiding a lot of "if" and how to solve the last 
>case ? My practical case takes functions with around 20 arguments.
>
>Thanks in advance,
>
>Sincerely.
>Stéphane DRAY
>-------------------------------------------------------------------------------------------------- 
>
>Département des Sciences Biologiques
>Université de Montréal, C.P. 6128, succursale centre-ville
>Montréal, Québec H3C 3J7, Canada
>
>Tel : (514) 343-6111 poste 1233         Fax : (514) 343-2293
>E-mail : stephane.dray at umontreal.ca
>-------------------------------------------------------------------------------------------------- 
>
>Web                                          http://www.steph280.freesurf.fr/
>
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Stéphane DRAY
-------------------------------------------------------------------------------------------------- 

Département des Sciences Biologiques
Université de Montréal, C.P. 6128, succursale centre-ville
Montréal, Québec H3C 3J7, Canada

Tel : (514) 343-6111 poste 1233         Fax : (514) 343-2293
E-mail : stephane.dray at umontreal.ca
-------------------------------------------------------------------------------------------------- 

Web                                          http://www.steph280.freesurf.fr/