[R] Variable scope in a function

[Gabor Grothendieck]

environment(test_func) <- baseenv()

will allow it to access the base environment so it can still find exists
but will not find kat.  If you issue the command

search()

then each attached package has the next as its parent and base is the
last one.

Regarding your second question, try rm().

f <- function() { x <- 1; rm(x); exists("x", environment()) }
f() # FALSE


On 9/4/07, thatsanicehatyouhave at mac.com <thatsanicehatyouhave at mac.com> wrote:
> Hello,
>
> I apologise in advance for this question; I'm sure it is answered in
> the documentation or this mailing list many times, however the answer
> has eluded me.
>
> I'm trying to write a function where I don't want external variables
> to be scoped in from the parent environment. Given this function:
>
> test_func = function() {
>
>        if (exists("kat") == FALSE) {
>                print("kat is undefined")
>        } else {
>                print(kat)
>        }
> }
>
> If I did this:
>
>  > kat = 12
>  > test_func()
>
> I'd like the result to be the error, but now it's 12 (which is of
> course correct according to the documentation).
>
> So there are two questions:
>
> 1) How can I disregard all variables from the parent environment
> within a function? (Although from what I've read on the mailing lists
> this isn't really what I want.)
>
> Apparently
>
> environment(test_func) = NULL
>
> is defunct, and what I thought was its replacement
>
> environment(test_func) = emptyenv()
>
> doesn't seem to be.
>
>
> 2) How can I "undefine" a variable, perhaps just within the context
> of my function. I'm hoping to find some line that I can put at the
> start of my function above so that the result would be:
>
>  > kat = 12
>  > test_func()
> [1] "kat is undefined"
>  > kat
> [1] 12
>
> Thanks in advance for any help!
>
> Cheers,
>
> Demitri
>
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