[R] Trying to learn how to write a function... can't define a variable??

[Berend Hasselman]

On 07-09-2012, at 21:32, William Dunlap wrote:

> Berend,
>  The OP's ADD() is returning the new value of x, as do all
> of your alternatives.  His problem is that he is not assigning
> the output of ADD to a variable, as in
>   z <- ADD(z)

> Ordinary functions do not alter their arguments.   There is
> no need for the 'x <-' in the definiton of ADD.  It may as
> well be defined as 
>  ADD <- function(x) x + 1
> 
> (One can write a replacement function, used as f(x)<-value,
> that modifies its first argument, but that is a more advanced topic.)

But then I don't understand this

z<-1
ADD<-function(x)
{
x<-x+1
}
ADD(z)

doesn't give any output.
But

z <- ADD(z)
z

gives

[1] 2

just as

ADD <- function(x) x+1
ADD(z)

does.

Berend