R help - Jun 2010 - exists() and functions

I'm a bit confused about how exists() work within a function -- I want
to test for unassigned variables, but I'm doing tests in the main
environment to figure out the function, so the variables DO exist in
the parent environment of a function call.

Why does:
myfunction <- function(variable_outside_function)
{
	print(exists("variable_outside_function",inherit=FALSE))
	print(exists("another_variable_outside_function",inherit=FALSE))
}

myfunction()

Return:
[1] TRUE
[1] FALSE

I didn't assign anything to variable_outside_function, so I'm unclear
why it thinks it exists...

--j

Always nice to answer my own question 3 minutes later.  The missing()
function does what I want.  Still, why DOES this exists() statement
fail?  Do functions "auto create" the variables once they are called,
regardless of whether or not they are assigned?

--j

On Fri, Jun 25, 2010 at 1:05 PM, Jonathan Greenberg
<greenberg at ucdavis.edu> wrote:
> I'm a bit confused about how exists() work within a function -- I want
> to test for unassigned variables, but I'm doing tests in the main
> environment to figure out the function, so the variables DO exist in
> the parent environment of a function call.
>
> Why does:
> myfunction <- function(variable_outside_function)
> {
> ? ? ? ?print(exists("variable_outside_function",inherit=FALSE))
> ? ? ?
?print(exists("another_variable_outside_function",inherit=FALSE))
> }
>
> myfunction()
>
> Return:
> [1] TRUE
> [1] FALSE
>
> I didn't assign anything to variable_outside_function, so I'm
unclear
> why it thinks it exists...
>
> --j
>