CODEWITHSUNDEEP
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Alex
Alex

Reputation: 15708

How to return elements of R list as independent objects in function environment?

Similar to this question:

Return elements of list as independent objects in global environment

I cannot seem to adapt the answer to assign the list elements when list2env is called inside a function:

E.g.

lst <- list(a = c(1, 2), b = c(3, 4))

tmp_fn <- function(lst) {
    # do computations on list elements
    # first assign each to the function environment
    list2env(lst, parent = parent.frame()) # fails

    # do stuff
    ...
}

I thought the parent = parent.frame() would work, but while debugging tmp_fn I only see that lst gets assigned to the function environment as a list, not the individual variables a and b.

Upvotes: 1

Views: 455

Answers (1)

G. Grothendieck
G. Grothendieck

Reputation: 269644

1) Use envir= here rather than parent= like this. Also, as shown, you may wish to add envir as an argument for flexibility:

lst <- list(a = c(1, 2), b = c(3, 4))

tmp_fn <- function(lst, envir = parent.frame()) {
    invisible(list2env(lst, envir = envir))
}
tmp_fn(lst)

2) Another possibility is to use list[...]<- from the gsubfn package (development version):

devtools::install_github("ggrothendieck/gsubfn")
library(gsubfn)

func <- function(lst) lst
list[a, b] <- func(lst)

Now a and b will be in the current environment.

Upvotes: 2

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