One simple way to make your example work is to define fx() in a place where its lexical scope includes the variables you want it to see:
> f <- function(fun, xx) {
+ x <- xx
+ fxx <- function() do.call(fun, list(y=3))
+ fx <- function(y) print(x*y)
+ fxx()
+ }
> x # verify that x is not a global variable!
Error: Object "x" not found
> f("fx", 13)
[1] 39
>Another way, that is probably more suited to what you want (since it sounds like you don't have control over where fx() is defined), is to make a local copy of fx(), and change its environment:
> fx <- function(y) print(x*y)
>
> f <- function(fun, xx) {
+ x <- xx
+ fxx <- function() do.call(fun, list(y=3))
+ fx <- fx
+ environment(fx) <- environment()
+ fxx()
+ }
> x # verify that x is not a global variable!
Error: Object "x" not found
> f("fx", 13)
[1] 39
>I suspect there is also some way to do this using eval() and its envir= and/or enclos= arguments, but I couldn't get anything like this to work.
The above solutions were generated by manual genetic programming (i.e., trial and error), so they may not be particularly good or elegant. However, I'm sure that others will point out both any problems with these suggestions and some better solutions!
hope this helps,
Tony Plate
At Wednesday 09:05 AM 3/10/2004, Thomas Petzoldt wrote:
Hello,
I want to call a function "fx" given by name, where some "global" variables (in the environment of fx) are passed to the function. For compatibility reasons I cannot modify the parameter list of fx and I want to avoid setting variables in the global environment (e.g. via <<-)
Is there a way, how to do this?
Thomas P.
The example:
fx <- function(y) print(x*y)
f <- function(fun, xx) { fxx <- function() {do.call(fun, list(y=3))} x <- x fxx() }
f("fx", 13)
## does not work, because fx does not find x
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