Allowing R functions to directly alter the parent environment

Question

I'm trying to figure out how to allow a function to directly alter or create variables in its parent environment, whether the parent environment is the global environment or another function.

For example if I have a function

my_fun <- function(){
  a <- 1
}

I would like a call to my_fun() to produce the same results as doing a <- 1.

I know that one way to do this is by using parent.frame as per below but I would prefer a method that doesn't involve rewriting every variable assignment.

my_fun <- function(){
  env = parent.frame()
  env$a <- 1
}

Why do you have the requirement to modify vars in parent env? — rbm, Feb 29 '16 at 13:46
I Agree with @jogo. What's the larger problem you're trying to solve? — Heroka, Feb 29 '16 at 13:46
`<<-` is the global modifier - but you should never do this. — kristang, Feb 29 '16 at 13:46
And `<<-` searches parent environment*s*, so would have different results in nested calls — rbm, Feb 29 '16 at 13:51
I'm performing some data analysis and have a few different functions which share some snippets of code and I want all or most of the intermediate values. I am cognisant that having functions break out of their calling environment is risky. — NGaffney, Feb 29 '16 at 14:07
Circle 6 of the R-inferno: http://www.burns-stat.com/pages/Tutor/R_inferno.pdf — jogo, Feb 29 '16 at 14:13

score 6 · Answer 1 · edited May 23 '17 at 12:23

Try with:

 g <- function(env = parent.frame()) with(env, { b <- 1 })

 g()

 b
 ## [1] 1

Note that normally it is preferable to pass the variables as return values rather than directly create them in the parent frame. If you have many variables to return you can always return them in a list, e.g. h <- function() list(a = 1, b = 2); result <- h() Now result$a and result$b have the values of a and b.

Also see Function returning more than one value.

Allowing R functions to directly alter the parent environment

1 Answers1