Using 'get' Inside Nested Functions on Local Variables

Question

I\'ve never quite gotten my head around nesting functions and passing arguments by reference. My strategy is typically to do something like get(\'variabletopassbyrefer

Answer 1

Also, pass the environment that the variables are located in. Note that parent.frame() refers to the environment in the currently running instance of the caller.

test1 <- function(a1, b1, env = parent.frame()) {

  a <- get(a1, env)
  b <- get(b1, env)
  c <- get('c', env)

  testvalue <- c * a * b

  testvalue

}

c <- 3
test2() # test2 as in question
## 6

Here a and b are in env c is not in env but it is in an ancestor of env and get looks through ancenstors as well.

ADDED Note that R formulas can be used to pass variable names with environments:

test1a <- function(formula) {
    v <- all.vars(formula)
    values <- sapply(v, get, environment(formula))
    prod(values)
}

test2a <- function() {
    a <- 1
    b <- 2
    test1a(~ a + b + c)
}

c <- 3
test2a()
## 6

REVISION: Corrected. Added comment. Added info on formulas.