R help - Mar 2009 - How to write a function that accepts unlimited number of input arguments?

Dear R-helpers:
I am an R newbie and have a question related to writing functions that
accept unlimited number of input arguments.
(I tried to peek into functions such as paste and cbind, but failed, I
cannot see their codes..)

Can someone kindly show me through a summation example?
Say, we have input scalar,  1 2 3 4 5
then the ideal function, say sum.test, can do
(1+2+3+4+5)==sum.test(1,2,3,4,5)

Also sum.test can work as the number of input scalar changes.

Many thanks in advance!

-sean

	[[alternative HTML version deleted]]

Hi,


On 9 Mar 2009, at 15:32, Sean Zhang wrote:
> Dear R-helpers:
> I am an R newbie and have a question related to writing functions that
> accept unlimited number of input arguments.
it's usually through the ... argument, e.g in paste(...).
> (I tried to peek into functions such as paste and cbind, but failed, I
> cannot see their codes..)
>
simply type their name in the R prompt

 > paste
function (..., sep = " ", collapse = NULL)
.Internal(paste(list(...), sep, collapse))
<environment: namespace:base>

etc...

but that's not very useful here.
> Can someone kindly show me through a summation example?
> Say, we have input scalar,  1 2 3 4 5
> then the ideal function, say sum.test, can do
> (1+2+3+4+5)==sum.test(1,2,3,4,5)
see ?Reduce for one way to do this:
add <- function(x) Reduce("+", x)
add(list(1, 2, 3))
>
> Also sum.test can work as the number of input scalar changes.
>
> Many thanks in advance!
>
> -sean
>
>        [[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.
_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag
______________________________


	[[alternative HTML version deleted]]

On 9 Mar 2009, at 16:04, Sean Zhang wrote:
> Dear Baptiste:
>
> Many thanks for your help!
>
> Using the Reduce way, it works almost perfectly.
> I ran into this problem when thinking of appending vectors.
> Is it possible to not use list() within add()
> so add(vec1,vec2,vec3) below can work?
add <- function(...) Reduce("+", list(...))
add(1, 2, 3)

> Also, do you have some  quick hints on using '...'?
>
> Many Thanks in advance.
>
I'm not sure of a good reference for this. I'd strongly suggest you  
read the Introduction to R manual ( also check the R project webpage  
for many other resources).

Also, it'd be better if you could Cc R-help next time you ask for  
further information.

Hope this helps,

baptiste
>
> vec1<-c(0,1)
> vec2<-c(2,3)
> vec3<-c(4,5)
> add <- function(x) Reduce("append", x)
> add(list(vec1, vec2))
> #add(vec1,vec2) does not work at the moment
>
> -sean
>
>
>
> On Mon, Mar 9, 2009 at 11:50 AM, baptiste auguie  
> <ba208@exeter.ac.uk> wrote:
> Hi,
>
>
> On 9 Mar 2009, at 15:32, Sean Zhang wrote:
>
>> Dear R-helpers:
>> I am an R newbie and have a question related to writing functions  
>> that
>> accept unlimited number of input arguments.
>
> it's usually through the ... argument, e.g in paste(...).
>
>> (I tried to peek into functions such as paste and cbind, but  
>> failed, I
>> cannot see their codes..)
>>
>
> simply type their name in the R prompt
>
> > paste
> function (..., sep = " ", collapse = NULL)
> .Internal(paste(list(...), sep, collapse))
> <environment: namespace:base>
>
> etc...
>
> but that's not very useful here.
>
>> Can someone kindly show me through a summation example?
>> Say, we have input scalar,  1 2 3 4 5
>> then the ideal function, say sum.test, can do
>> (1+2+3+4+5)==sum.test(1,2,3,4,5)
>
> see ?Reduce for one way to do this:
> add <- function(x) Reduce("+", x)
> add(list(1, 2, 3))
>>
>> Also sum.test can work as the number of input scalar changes.
>>
>> Many thanks in advance!
>>
>> -sean
>>
>>        [[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.
>
> _____________________________
>
> Baptiste Auguié
>
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> Phone: +44 1392 264187
>
> http://newton.ex.ac.uk/research/emag
> ______________________________
>
>
_____________________________

Baptiste Auguié

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag
______________________________


	[[alternative HTML version deleted]]

Try this:

sum.test <- function(...) sum(c(...))

More commonly one uses the list(...) construct.

On Mon, Mar 9, 2009 at 11:32 AM, Sean Zhang <seanecon at gmail.com>
wrote:
> Dear R-helpers:
> I am an R newbie and have a question related to writing functions that
> accept unlimited number of input arguments.
> (I tried to peek into functions such as paste and cbind, but failed, I
> cannot see their codes..)
>
> Can someone kindly show me through a summation example?
> Say, we have input scalar, ?1 2 3 4 5
> then the ideal function, say sum.test, can do
> (1+2+3+4+5)==sum.test(1,2,3,4,5)
>
> Also sum.test can work as the number of input scalar changes.
>
> Many thanks in advance!
>
> -sean
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
>