sys.frame() and variables from parent frame
On Feb 27, 2013, at 1:11 AM, Z? Miguel wrote:
Dear David,
thanks for your reply. Sorry for the ambiguous example. I guess the get() will do it, but I still have a question regarding the parent frame. If I declare both function g and f in the global environment:
g <- function()
{
get(N,envir = ???)
write(N)
}
f<-function()
{
N<-99
g()
}
What is the environment I should be evoking in the get() function? Excuse me for the bad coding, I jst migrated from another language, please interpret it as a generic language.
You can specify the global environment with either a function call or by a consant name
globalenv()
.GlobalEnv
In your code however, 'N' is not in the global environment and you are not passing a character argument to get() as you had been in your first example. Furthermore you have chosen to use write which does not gte the desired effect of reporting from inside a function.
g <- function()
{
get("N", envir = .GlobalEnv) # character argument to get
cat(N)
}
f<-function()
{
N<-99 # not in the global environment
g()
}
N <- 42 # assigned in the global environment
f()
# returns 42
David.
> Cheers,
>
> Jos?
>
>
>
>
> On 27 February 2013 01:20, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Feb 26, 2013, at 2:40 AM, Jos? 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
>
>
>
>
> --
> Jos? Miguel Delgado
> Reichenberger Str. 52
> 10999 Berlin
> Tel. 0176 9633 92 56
David Winsemius
Alameda, CA, USA