[R] Appropriate method for sharing data across functions

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of John C Nash
> Sent: Thursday, April 05, 2012 1:20 PM
> To: r-help at r-project.org
> Subject: [R] Appropriate method for sharing data across functions
> 
> In trying to streamline various optimization functions, I would like to have a scratch pad
> of working data that is shared across a number of functions. These can be called from
> different levels within some wrapper functions for maximum likelihood and other such
> computations. I'm sure there are other applications that could benefit from this.
> 
> Below are two approaches. One uses the <<- assignment to a structure I call OPCON. The
> other attempts to create an environment with this name, but fails. Though I have looked
> at
> a number of references, I have so far not found an adequate description of how to
> specify
> where the OPCON environment is located. (Both the green and blue books do not cover
> this
> topic, at least not under "environment" in the index.)
> 
> Is there a recommended approach to this? I realize I could use argument lists, but they
> get long and tedious with the number of items I may need to pass, though passing the
> OPCON
> structure in and out might be the proper way.

Make OPCON an environment and pass it into the functions that may read it or alter it.  There
is no real need to pass it out, since environments are changed in-place (unlike lists).  E.g.,
  > x <- list2env(list(one=1, two="ii", three=3))
  > x
  <environment: 0x0000000003110890>
  > objects(x)
  [1] "one"   "three" "two"  
  > x[["two"]]
  [1] "ii"
  > with(x, three+one)
  [1] 4
  > f <- function(z, env) { env[["newZ"]] <- z ; sqrt(z) }
  > f(10, x)
  [1] 3.162278
  > x[["newZ"]] # put there by f()
  [1] 10

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> An onAttach() approach was suggested by
> Paul
> Gilbert and tried, but it has so far not succeeded and, unfortunately, does not seem to be
> usable from source() i.e., cannot be interpreted but must be built first.
> 
> JN
> 
> Example using <<-
> 
> rm(list=ls())
> optstart<-function(npar){ # create structure for optimization computations
>     # npar is number of parameters ?? test??
>     OPCON<<-list(MAXIMIZE=TRUE, PARSCALE=rep(1,npar), FNSCALE=1,
>         KFN=0, KGR=0, KHESS=0)
>     # may be other stuff
>     ls(OPCON)
> }
> 
> add1<-function(){
>     OPCON$KFN<<-1+OPCON$KFN
>     test<-OPCON$KFN
> }
> 
> OPCON<<-list(MAXIMIZE=TRUE, PARSCALE=rep(1,4), FNSCALE=1,
>         KFN=0, KGR=0, KHESS=0)
> ls(OPCON)
> print(add1())
> print(add1())
> print(ls.str())
> 
> rm(OPCON) # Try to remove the scratchpad
> print(ls())
> 
> tmp<-readline("Now try from within a function")
> setup<-optstart(4) # Need to sort out how to set this up appropriately
> cat("setup =")
> print(setup)
> 
> print(add1())
> print(add1())
> 
> rm(OPCON) # Try to remove the scratchpad
> 
> ======================
> Example (failing) using new.env:
> 
> rm(list=ls())
> optstart<-function(npar){ # create structure for optimization computations
>     # npar is number of parameters ?? test??
>     OPCON<-new.env(parent=globalenv())
>     OPCON<-list(MAXIMIZE=TRUE, PARSCALE=rep(1,npar), FNSCALE=1,
>         KFN=0, KGR=0, KHESS=0)
>     # may be other stuff
>     ls(OPCON)
> }
> 
> add1<-function(){
>     OPCON$KFN<-1+OPCON$KFN
>     test<-OPCON$KFN
> }
> 
> OPCON<-new.env(parent=globalenv())
> OPCON<-list(MAXIMIZE=TRUE, PARSCALE=rep(1,4), FNSCALE=1,
>         KFN=0, KGR=0, KHESS=0)
> ls(OPCON)
> print(add1())
> print(add1())
> print(ls.str())
> 
> rm(OPCON) # Try to remove the scratchpad
> print(ls())
> 
> tmp<-readline("Now try from within a function")
> setup<-optstart(4) # Need to sort out how to set this up appropriately
> cat("setup =")
> print(setup)
> 
> print(add1())
> print(add1())
> 
> rm(OPCON) # Try to remove the scratchpad
> 
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