[R] function parameters - testing
Sundar Dorai-Raj
sundar.dorai-raj at pdf.com
Fri Jun 9 22:06:07 CEST 2006
Larry Howe wrote:
> Hello,
>
> I am trying to test a function argument to see if it is or is not a useful
> number. However I cannot seem to find a test that works. For example
>
>
>>f = function(x) {
>
> + print(exists("x"))
> + print(is.null(x))
> + }
>
>>rm(x)
>>f(z)
>
> [1] TRUE
> Error in print(is.null(x)) : Object "z" not found
>
> exists gives TRUE, but then any other kind of test I try to run gives me an
> error. I need a test for existence that will work inside a function.
>
> Larry Howe
>
This works because "x" exists in the function "f". Perhaps you want this
instead?
f <- function(x) {
print(deparse(substitute(x)))
print(exists(deparse(substitute(x))))
print(is.null(x))
invisible()
}
z <- 2
f(z)
rm(z)
f(z)
Also, see the "where" argument in ?exists.
HTH,
--sundar
More information about the R-help
mailing list