R help - Apr 2006 - environment

Hi,

Consider the code :

g <- function(){
  print(.x)
 .x <- 3
}

f <- function(){
  environment(g) <- environment()
  .x <- 2
  g()
  .x
}

 > f()
[1] 2
[1] 2


I would like f() to return 3. How can I do that ? Am I completely out of 
place ?
Doing that, I want to avoid to pass .x as a parameter in f, because in 
real life .x is pretty big and g() is called over and over in a loop.

Thanks

Romain

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| Romain FRANCOIS - http://francoisromain.free.fr               |
| Doctorant INRIA Futurs / EDF                                  |
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Romain Francois <francoisromain at free.fr> writes:
> Hi,
> 
> Consider the code :
> 
> g <- function(){
>   print(.x)
>  .x <- 3
> }
> 
> f <- function(){
>   environment(g) <- environment()
>   .x <- 2
>   g()
>   .x
> }
> 
>  > f()
> [1] 2
> [1] 2
> 
> 
> I would like f() to return 3. How can I do that ? Am I completely out of 
> place ?
> Doing that, I want to avoid to pass .x as a parameter in f, because in 
> real life .x is pretty big and g() is called over and over in a loop.
If you want to assign into the environment of g, you'll need <<- ,
otherwise you  assign to a local variable. 

Another possibility involves assign(..., parent.frame()) 

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On Wed, 26 Apr 2006, Romain Francois wrote:
> Hi,
>
> Consider the code :
>
> g <- function(){
>  print(.x)
> .x <- 3
> }
>
> f <- function(){
>  environment(g) <- environment()
>  .x <- 2
>  g()
>  .x
> }
>
> > f()
> [1] 2
> [1] 2
>
>
> I would like f() to return 3. How can I do that ? Am I completely out of
> place ?
> Doing that, I want to avoid to pass .x as a parameter in f, because in
> real life .x is pretty big and g() is called over and over in a loop.
>
As long as .x doesn't get modified it probably won't be copied, so this
is
unlikely to make any difference to memory use even if you work out how to 
do it.

 	-thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle