R help - Jan 2006 - Putting an object in to a function that calls the current function

Hello!

I would like to put an object in to a function that calls the current
function.

I thought the answer will be clear to me after reading the help files:
?assign
?sys.parent

However it is not.
Here is an example I thought should work, however it dose not exactly:

f<-function(){s();print(a)}
s<-function()assign(x="a",value="ok",pos=sys.parent())
f() #I want to get "ok"
a #I do not want "a" in global enviorment, so here I should get 
#Error: Object "a" not found
ff<-function()f() #here I also want to get "ok" - it should not
matter if
the parent fuction has any parents

Thank you in advance for suggestions!

Ales Ziberna

Check out:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/64929.html

On 1/4/06, Ales Ziberna <aleszib at gmail.com>
wrote:
> Hello!
>
> I would like to put an object in to a function that calls the current
> function.
>
> I thought the answer will be clear to me after reading the help files:
> ?assign
> ?sys.parent
>
> However it is not.
> Here is an example I thought should work, however it dose not exactly:
>
> f<-function(){s();print(a)}
>
s<-function()assign(x="a",value="ok",pos=sys.parent())
> f() #I want to get "ok"
> a #I do not want "a" in global enviorment, so here I should get
> #Error: Object "a" not found
> ff<-function()f() #here I also want to get "ok" - it should
not matter if
> the parent fuction has any parents
>
> Thank you in advance for suggestions!
>
> Ales Ziberna
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>

On 1/4/2006 9:14 AM, Ales Ziberna wrote:
> Hello!
> 
> I would like to put an object in to a function that calls the current
> function.
> 
> I thought the answer will be clear to me after reading the help files:
> ?assign
> ?sys.parent
> 
> However it is not.
> Here is an example I thought should work, however it dose not exactly:
> 
> f<-function(){s();print(a)}
>
s<-function()assign(x="a",value="ok",pos=sys.parent())
> f() #I want to get "ok"
> a #I do not want "a" in global enviorment, so here I should get 
> #Error: Object "a" not found
> ff<-function()f() #here I also want to get "ok" - it should
not matter if
> the parent fuction has any parents
> 
> Thank you in advance for suggestions!
That's not a good idea.  Why would you want to do something like that?

That out of the way, here's a function that does it:

f<-function(){s();print(a)}
s<-function()assign(x="a",value="ok",env=parent.frame())

The difference between pos=sys.parent() and env=parent.frame() is that 
the pos is interpreted as a position in the search list (see ?assign), 
while parent.frame() gives you the environment from the stack, 
equivalent to sys.frame(sys.parent()).

In R you're almost certainly better off working directly with 
environments, rather than going through integer indexing the way you 
(used to?) have to do in S-PLUS.

Did I mention that messing with the environment of your caller is a bad 
idea?  It's not yours, don't touch it.

Duncan Murdoch