[R] variable scope

[R. Michael Weylandt]

On Tue, Aug 28, 2012 at 1:29 PM, Sam Steingold <sds at gnu.org> wrote:
> At the end of a for loop its variables are still present:
>
> for (i in 1:10) {
>   x <- vector(length=100000000)
> }
> ls()
>
> will print "i" and "x".
> this means that at the end of the for loop body I have to write
>
>   rm(x)
>   gc()
>
> is there a more elegant way to handle this?

Wrap the loop in local() scope perhaps? This might get tricky if you
need to save some results from the loop, but I think you're ok if they
are initialized outside the loop and you use super-assignment. Almost
always you shouldn't need manual garbage collection.

Something like: # Terribly impractical, but gets the point across

y <- numeric(100)
local({
  for(i in 1:10){
      x <- rnorm(10)
      y[10*(i-1) + 1:10] <<- x
  }
})

print(x) # Error
print(y)

Doubt that works out to be significantly more elegant however.

Michael

>
> Thanks.
>
> --
> Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X 11.0.11103000
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