[R] sys.frame() and variables from parent frame

[David Winsemius]

On Feb 26, 2013, at 2:40 AM, José Miguel Delgado wrote:

> Dear R-help,
> 
> I wrote the following lines in order to use a variable from a parent frame in my callM() function. I would like to solve this by only editing the callM(function). When I run this code I obtain a empty list, meaning that eval(ls(),sys.frame(-1)) could not access the variables in the parent function. Any suggestions? Thanks in advance!
> 
> metaCall <- function()
>  {
>    NN <- 99
>    callM()
>    }
> 
> callM <- function()
>  {
>    Ls <- eval(ls(),sys.frame(-1))
>    print(Ls)
>    ### use Ls to call a certain model named M

That doesn't make much sense.

>    }
> 
> metaCall()
> 

I don't think you need the eval() call:

 metaCall <- function()
 {
   NN <- 99
   callM()
   }

callM <- function()
 {
   Ls <- ls(env=sys.frame(-1))
   cat(Ls)
   }

metaCall()
NN

You should be aware that metaCall will not return anything since the last value is from the cat()-call or the print()-call and they each return NULL. If you wanted to go on from there and do something with 'NN", which is no longer a number but rather a character vector, you could, however.

Oh, I think I finally see .... the eval() was an attempt to retrieve  the object named "NN"" in the parent.frame? That means you need :

?get

metaCall <- function()
 {
   NN <- 99
   callM()
   }

callM <- function()
 {
   Ls <- ls(env=sys.frame(-1))
   str(get(Ls, env=sys.frame(-1)))
   }

metaCall()
# num 99

-- 
David Winsemius
Alameda, CA, USA