[R] Equivalent of S> assign( , ,frame=1)

[Thomas Lumley]

On Thu, 27 Apr 2000, Olivier Renaud wrote:

> Hi,
> I'm new to R, and I certainly miss an obvious point. I looked in the doc
> and the archieve, but could not find what is the R equivalent of the S
> assign( , ,frame=1). I guess the question is like what is the equivalent
> of the S frames and how to access them. As an example: 

R doesn't have an equivalent of frame 1.  It is possible to store objects
in an environment, which can either be referenced by a variable or stored
in the search path.

So one way to do this is

attach(NULL,name="Frame1")
initial <-function() 
  {
   frame1<-match("Frame1",search())
   assign ("x", 2, env=frame1)
   assign ("y", 3, env=frame1)
   }
   
YOu can now refer to x anywhere.  It does not override a variable called
'x' in the global environment, though.

Alternatively you can store things in an environment off the search path
and explicitly refer to them by location

frame1<-new.env()
initial <-function()   {
   assign ("x", 2, env=frame1)
   assign ("y", 3, env=frame1)
   }

subrout<-function(){
	get("x",env=frame1)+get("y",env=frame1)		
}
 

Alternatively, you can just pass things explicitly into the
functions. There isn't much efficiency loss, as arguments aren't copied
unless they are modified.


	-thomas


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle


> oneprog <- function()
> {
>   initial()
>   res <- subrout()
>   return(res)
>   }
> 
> initial <- function()
>   {
>   assign ("x", 2, frame=1)
>   assign ("y", 3, frame=1)
>   }
> 
>   
> subrout <- function()
>   return(x+y)
> 
> This works perfectly with S. I know that if I put subrout inside oneprog
> and replace the call to initial by a simple x <- 2;y <-3, it will work
> on R (and not on S). But initial is a routine I use in many different
> programs, and therefore I don't want it inside a given one. Any help?
> More general comments on this way of programming are also welcomed.
> 
> 
> Olivier
> -- 
> Olivier Renaud
> Department of Statistics  -  Sequoia Hall  -  390 Serra Mall
> STANFORD, CA, 94305-4065     mailto:renaud at stat.stanford.edu
>                              http://www.stanford.edu/~renaud
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