R devel - Mar 2009 - linking environments

Dear R-helpers,

I try to use nested R-functions as follows:

help1 = function(){
        x = 1
        help2()
}

with

help2 = function(){
        if (x == 1)
                cat("Hello world x = 1")
}

If I compile these functions and run help1()
an error message occurs
        Fehler in help2() : objekt "x" nicht gefunden

in english "error in help2(): object "x" not found"

If I change help1 to

help1 = function(){
        x <<- 1
        help2()
}

so that "x" is now defined at the global environment it works fine.
But the problem is, now "x" is defined also outside of help1 and this
is
not desired !

Is there any usable solution for this problem?
But, the original problem is to assign new values for "x" in help1
inside
help2 !

Thanks in advance
 
Jörg Betzin
---------------------------------------------------
Deutsches Zentrum für Altersfragen
Manfred-von-Richthofen-Str. 2
12101 Berlin
Tel. (030) 260740-20
E-Mail: joerg.betzin@dza.de
URL: http://www.dza.de
---------------------------------------------------

	[[alternative HTML version deleted]]

On 3/25/2009 11:47 AM, Joerg Betzin wrote:
> Dear R-helpers,
> 
> I try to use nested R-functions as follows:
You didn't use nested functions.  They would look like this:

  help1 <- function(){
      help2 <- function(){
          if (x == 1)
                  cat("Hello world x = 1")
      }

      x <- 1
      help2()
  }

Because help2 is now nested within help1, it can see all the local 
variables in help1, so things work with it done this way.

There are tricks to define help2 outside of help1 but allow it to see 
the variables within there, but I'd keep it simple and avoid them.

Duncan Murdoch
> 
> help1 = function(){
>         x = 1
>         help2()
> }
> 
> with
> 
> help2 = function(){
>         if (x == 1)
>                 cat("Hello world x = 1")
> }
> 
> If I compile these functions and run help1()
> an error message occurs
>         Fehler in help2() : objekt "x" nicht gefunden
> 
> in english "error in help2(): object "x" not found"
> 
> If I change help1 to
> 
> help1 = function(){
>         x <<- 1
>         help2()
> }
> 
> so that "x" is now defined at the global environment it works
fine.
> But the problem is, now "x" is defined also outside of help1 and
this is
> not desired !
> 
> Is there any usable solution for this problem?
> But, the original problem is to assign new values for "x" in
help1 inside
> help2 !
> 
> Thanks in advance
>  
> J?rg Betzin
> ---------------------------------------------------
> Deutsches Zentrum f?r Altersfragen
> Manfred-von-Richthofen-Str. 2
> 12101 Berlin
> Tel. (030) 260740-20
> E-Mail: joerg.betzin at dza.de
> URL: http://www.dza.de
> ---------------------------------------------------
> 
> 	[[alternative HTML version deleted]]
> 
> 
> 
> ------------------------------------------------------------------------
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

> 
> -----Original Message-----
> From: r-devel-bounces at r-project.org on behalf of Joerg Betzin
> Sent: Wed 3/25/2009 8:47 AM
> To: r-devel at r-project.org
> Subject: [Rd] linking environments
>  
> Dear R-helpers,
> 
> I try to use nested R-functions as follows:

Looks like a question for R-help, not R-devel.
It's better to post such questions to the
R-help at r-project.org mailing list.

> 
> help1 = function(){
>         x = 1
>         help2()
> }
> 
> with
> 
> help2 = function(){
>         if (x == 1)
>                 cat("Hello world x = 1")
> }
> 
> If I compile these functions and run help1()
> an error message occurs
>         Fehler in help2() : objekt "x" nicht gefunden
> 
> in english "error in help2(): object "x" not found"
> 
Why not pass the value of x from help1
to help2?

help1 <- function(){
        x <- 1
        help2(x)
}



help2 <- function(x){
        if (x == 1)
                cat("Hello world x = 1")
}



> help1 <- function(){
+         x <- 1
+         help2(x)
+ }
> 
> 
> 
> help2 <- function(x){
+         if (x == 1)
+                 cat("Hello world x = 1")
+ }
> 
> 
> 
> help1()
Hello world x = 1> 



(No compiling is involved.)
> If I change help1 to
> 
> help1 = function(){
>         x <<- 1
>         help2()
> }
> 
> so that "x" is now defined at the global environment it works
fine.
> But the problem is, now "x" is defined also outside of help1 and
this is
> not desired !
> 
> Is there any usable solution for this problem?
> But, the original problem is to assign new values for "x" in
help1 inside
> help2 !
Is this a homework problem?

Some reading of 
?environment
will help answer this.
> 
> Thanks in advance
>  
> J?rg Betzin
> ---------------------------------------------------
> Deutsches Zentrum f?r Altersfragen
> Manfred-von-Richthofen-Str. 2
> 12101 Berlin
> Tel. (030) 260740-20
> E-Mail: joerg.betzin at dza.de
> URL: http://www.dza.de
> ---------------------------------------------------
> 
> 	[[alternative HTML version deleted]]
> 


Steven McKinney, Ph.D.

Statistician
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British Columbia Cancer Research Centre

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