R help - Nov 2011 - How do I query "..." in a function call?

This is probably a very noobish question, but if I want to create a
function that allows an undetermined number of, say, numeric vectors to be
fed to it, I would use:

myfunction = function(...)
{
# Do something

}

Right?  If so, how do I a) count the number of vectors "fed" to the
function, and b) how do I treat those vectors as variables, e.g. for the
call:

myfunction(c(1:10),c(2:11),c(3:13))

Thanks!

--j

-- 
Jonathan A. Greenberg, PhD
Assistant Professor
Department of Geography
University of Illinois at Urbana-Champaign
607 South Mathews Avenue, MC 150
Urbana, IL 61801
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307@hotmail.com, Gchat: jgrn307, Skype: jgrn3007
http://www.geog.illinois.edu/people/JonathanGreenberg.html

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You can do something like this:

test <- function(x,...){
     print(x)
     args = list(...)
     if('y' %in% names(args))print(args$y)
     if('z' %in% names(args))print(args$z) 
}

Regards
S?ren

________________________________________
Fra: r-help-bounces at r-project.org [r-help-bounces at r-project.org]
P&#229; vegne af Jonathan Greenberg [jgrn at illinois.edu]
Sendt: 21. november 2011 23:18
Til: r-help
Emne: [R] How do I query "..." in a function call?

This is probably a very noobish question, but if I want to create a
function that allows an undetermined number of, say, numeric vectors to be
fed to it, I would use:

myfunction = function(...)
{
# Do something

}

Right?  If so, how do I a) count the number of vectors "fed" to the
function, and b) how do I treat those vectors as variables, e.g. for the
call:

myfunction(c(1:10),c(2:11),c(3:13))

Thanks!

--j

--
Jonathan A. Greenberg, PhD
Assistant Professor
Department of Geography
University of Illinois at Urbana-Champaign
607 South Mathews Avenue, MC 150
Urbana, IL 61801
Phone: 415-763-5476
AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307, Skype: jgrn3007
http://www.geog.illinois.edu/people/JonathanGreenberg.html

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______________________________________________
R-help at r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Hi Jonathan,

On Mon, Nov 21, 2011 at 5:18 PM, Jonathan Greenberg <jgrn at illinois.edu>
wrote:
> This is probably a very noobish question, but if I want to create a
> function that allows an undetermined number of, say, numeric vectors to be
> fed to it, I would use:
>
> myfunction = function(...)
> {
> # Do something
>
> }
>
> Right? ?If so, how do I a) count the number of vectors "fed" to
the
> function, and b) how do I treat those vectors as variables, e.g. for the
> call:
>
> myfunction(c(1:10),c(2:11),c(3:13))
`args <- list(...)` will create a list out of the "things" passed
through in `...`

For example:

myfunction <- function(...) {
  args <- list(...)
  length(args) ## this is how many things were passed in
  names(args) ## these are the variable names used
  ## etc.
}

HTH,
-steve

-- 
Steve Lianoglou
Graduate Student: Computational Systems Biology
?| Memorial Sloan-Kettering Cancer Center
?| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact

Hi: You can make a list out of the ... by doing below.

myfunction = function(...)
{
params <- list(...)
print(params)
print(str(params))
}

On Mon, Nov 21, 2011 at 5:18 PM, Jonathan Greenberg
<jgrn@illinois.edu>wrote:
> This is probably a very noobish question, but if I want to create a
> function that allows an undetermined number of, say, numeric vectors to be
> fed to it, I would use:
>
> myfunction = function(...)
> {
> # Do something
>
> }
>
> Right?  If so, how do I a) count the number of vectors "fed" to
the
> function, and b) how do I treat those vectors as variables, e.g. for the
> call:
>
> myfunction(c(1:10),c(2:11),c(3:13))
>
> Thanks!
>
> --j
>
> --
> Jonathan A. Greenberg, PhD
> Assistant Professor
> Department of Geography
> University of Illinois at Urbana-Champaign
> 607 South Mathews Avenue, MC 150
> Urbana, IL 61801
> Phone: 415-763-5476
> AIM: jgrn307, MSN: jgrn307@hotmail.com, Gchat: jgrn307, Skype: jgrn3007
> http://www.geog.illinois.edu/people/JonathanGreenberg.html
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> 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.
>
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