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phonixor
phonixor

Reputation: 1693

how to remove a variable from inside a function in R

i am trying to create a function in which i want to remove one of the variables passed to it.

now R works in annoying ways in that it copies the object instead of giving a reference. (technically the copying only happens if you make a change... but meh...)

a=function(b){
  rm(b)
  # rm(b)
}
test=123
a(test) # will remove b, not test
# you can verify that by adding the 2nd rm(b)

i tried

a=function(b){
  rm(match.call()[[2]])
}

but that gives the error:

 Error in rm(match.call()[[3]]) : 
  ... must contain names or character strings

Upvotes: 2

Views: 2213

Answers (2)

Carl Witthoft
Carl Witthoft

Reputation: 21502

similar to nrussell's answer, here's the line from cgwtools::askrm which does an arbitrary function call on the selected object:

call(fn, as.name(thenam)), envir = parent.frame(1))

(and, yes, I'm plugging my own toolkit here :-) )

Upvotes: 0

nrussell
nrussell

Reputation: 18602

Try this:

Foo <- function(x){
  Sx <- deparse(substitute(x))
  rm(list=Sx,envir=sys.frame(-1))
}
##
Z <- 123
ls()
##
[1] "Foo" "Z" 
##
Foo(x=Z)
ls()
[1] "Foo"

Upvotes: 3

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