[R] Environment question

[William Dunlap]

Make a new environment for each function and populate it with
the variables that your functions require.  local() is a convenient
way to do this:

f.factory3 <- function(destinationEnvir = globalenv())
{
  for (y in 2:3) {
    fname <- paste("plus", y, sep = ".")
    f <- local(function(x) x + y, envir=list2env(list(y=y),
parent=destinationEnvir))
    assign(fname, f, envir = destinationEnvir)
  }
}


Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Nov 13, 2015 at 9:53 AM, ALBERTO VIEIRA FERREIRA MONTEIRO
<albmont at centroin.com.br> wrote:
> I have another environment question.
>
> I understand why this works as expected:
>
> f.factory <- function()
> {
>   y <- 2
>   fname <- paste("plus", y, sep = ".")
>   f <- function(x) x + y
>   assign(fname, f, envir = globalenv())
> }
>
> f.factory()
> plus.2(2) # 4
>
> and I also understand why this does NOT work:
>
> f.factory <- function()
> {
>   for (y in 2:3) {
>     fname <- paste("plus", y, sep = ".")
>     f <- function(x) x + y
>     assign(fname, f, envir = globalenv())
>   }
> }
>
> f.factory()
> plus.2(2) # 5
>
> (the reason is that both plus.2 and plus.3 have the
> same environment as f.factory when f.factory terminates,
> which assign 2 to variable y in the first case and 3 in
> the second case)
>
> However, I don't know an elegant way to adapt f.factory
> so that it works as expected. Any suggestions?
>
> Alberto Monteiro
>
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