Re: [R] Testing for existence inside a function

From: Alberto Monteiro <albmont_at_centroin.com.br>
Date: Tue, 15 May 2007 17:06:15 -0200

Talbot Katz wrote:
>
> I'm having trouble testing for existence of an object inside a function.
>
No, you are having trouble testing for existence of an object _before_ the function is called :-)

> Suppose I have a function:
>
> f<-function(x){
> ...
> }
>
> and I call it with argument y:
>
> f(y)
>
> I'd like to check inside the function whether argument y exists.
>
This can't be done, because the error happens before f is called.

Try this:

f <- function(x) x + 1
f(y.does.not.exist)
y.does.not.exist

The error message is (almost) the same, and it happens when parsing the line. There's no way to change f to change this.

Alberto Monteiro



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