[R] optional fields in function declarations

Adaikalavan Ramasamy ramasamy at cancer.org.uk
Sun May 20 01:21:32 CEST 2007

Can you provide an simple example of what you want the function to do?

Generally, I set some value in the default.

raise <- function(x, power=1){ return( x^power ) }

 > raise(5)
[1] 5
 > raise(5,3)
[1] 125

Or you can do the same but in a slightly unclear manner.

raise <- function(x, power){
   if(missing(power)) power <- 1
   return( x^power )

I prefer the former.

Regards, Adai

claudio.is at libero.it wrote:
> Dear R users,
> I need to create a set of function to solve some tasks. I want to leave the operator to decide whether uses default parameters or change it; so the functions may have some optional fields. I tied to use the function missing(), but it will work properly only if the optional field is decleared at last in the function.
> Can you give me some suggestion an some reference?
> thank you.
> Claudio
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