[R] Testing for arguments in a function

[Gabor Grothendieck]

On Mon, Sep 26, 2011 at 3:39 PM, Gene Leynes <gleynes at gmail.com> wrote:
> I don't understand how this function can subset by i when i is missing....
>
> ## My function:
> myfun = function(vec, i){
>    ret = vec[i]
>    ret
> }
>
> ## My data:
> i = 10
> vec = 1:100
>
> ## Expected input and behavior:
> myfun(vec, i)
>
> ## Missing an argument, but error is not caught!
> ## How is subsetting even possible here???
> myfun(vec)
>
>
> Is there a way to check for missing function arguments, *and* which function
> arguments are missing?
>

R lets you pass missing arguments down from one function call to
another in such a way that they retain their missingness:

> f <- function(x) g(x)
> g <- function(x) missing(x)
> f()
[1] TRUE

-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com