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
>
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>
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_____________________________

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
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