[R] Global variables

Duncan Murdoch murdoch.duncan at gmail.com
Thu Jan 6 22:59:08 CET 2011

On 06/01/2011 4:45 PM, Sebastien Bihorel wrote:
> Dear R-users,
> Is there a way I can prevent global variables to be visible within my
> functions?

Yes, but you probably shouldn't.  You would do it by setting the 
environment of the function to something that doesn't have the global 
environment as a parent, or grandparent, etc.  The only common examples 
of that are baseenv() and emptyenv().  For example,

x <- 1
f <- function() print(x)

Then f() will work, and print the 1.  But if I do

environment(f) <- baseenv()

then it won't work:

 > f()
Error in print(x) : object 'x' not found

The problem with doing this is that it is not the way users expect 
functions to work, and it will probably have weird side effects.  It is 
not the way things work in packages (even packages with namespaces will 
eventually search the global environment, the namespace just comes 
first).  There's no simple way to do it and yet get access to functions 
in other packages besides base without explicitly specifying them (e.g. 
you'd need to use stats::lm(), not just lm(), etc.)

Duncan Murdoch

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