Defining environments within functions

Duncan,

    Sorry to be, well, nit picking, but I can't get your example to run. I 
am a longtime Splus user and am only using R on the side. The concept of 
environments is one I have yet to grasp. I think the example you are trying 
to provide will illuminate things for me, but it doesn't source. The 
definition of fnBuilder sources fine, though I am not sure what the 
"commonArgs <- ..." is meant to do. Anyway, calling:
  

both <- fnBuilder(...)
    

Error: '...' used in an incorrect context

and so I though, maybe you meant:

  

both <- fnBuilder(c(1,2,3))
    

Error in fnBuilder(c(1, 2, 3)) : '...' used in an incorrect context

But then I thought you were perhaps using "..." as a placeholder not as 
syntax and so I have little idea what it is you are trying to show. Could 
you clarify what your example is demonstrating in regards to scoping?

    So far, I have found the only part of R my Splus knowledge doesn't 
translate is in regard to this sort of thing. I can't tell you how much pain 
translating "substitute" idioms into R has caused me. Thanks,

    Matt




----- Original Message ----- 
From: "Duncan Murdoch" <murdoch at stats.uwo.ca>
To: <gjh27 at cornell.edu>
Cc: <r-devel at r-project.org>
Sent: Thursday, August 28, 2008 5:42 AM
Subject: Re: [Rd] Defining environments within functions


  

Giles Hooker wrote:
    

How can I define environments within a function so that they are visible
to calls to a sub-function?

      

I think you need to give a simplified, runnable example.  (Or at least 
runnable until it hits the scoping problem you've got.)  "Sub-function" 
isn't R terminology, and it's not clear what you mean by it.

In R, you rarely need to work with environments explicitly.  You just 
define functions in the same location and they share the same environment. 
For example,

fnBuilder <- function(commonArgs) {
 commonVars <- ...
 ProfileErr <- function(params, ...) {}
 coefs <- function(params, ...) {}
 return(list(ProfileErr, coefs))
}

both <- fnBuilder(...)
ProfileErr <- both[[1]]
coefs <- both[[2]]

Now ProfileErr and coefs share the same environment, and both can see (and 
modify) commonArgs and commonVars.

Duncan Murdoch


    

I have defined an objective function,

ProfileErr = function(params,...)

which I would like to optimize using standard routines (optim,
nlminb,....) but which contains auxiliary variables which need to be
updated along with params. No optimization routine in R that I have
found has facilities for this.

Specifically, within ProfileErr, I need to calculate

  coefs(params,...)

This a function which requires a further optimization, and I can achieve
significant efficiency gains by starting  where the last optimization
ended, so I would like to keep track of it.

At the command line, I get around this by

ProfileEnv = new.env()
assign('coefs',coefs,3,ProfileEnv)

and within ProfileErr, I can call

startcoefs = get('coefs',envir=ProfileEnv)
* do the optimization to get newcoefs *
assign('coefs',newcoefs,3,ProfileEnv)

Then calling

optim(pars,ProfileErr,....)

works fine. However, when I try to wrap all of that in its own function

profile.estimate = fn(pars,...){
ProfileEnv = new.env()
assign('coefs',coefs,3,ProfileEnv)

res = optim(pars,ProfileErr,....)
}


ProfileErr no longer sees ProfileEnv. I haven't been able to make much
sense out of the documentation on environments, but is there a way to
make this work? Otherwise I'm back to writing variables out to files.

Many thanks,

Giles