How do you use “<<-” (scoping assignment) in R?

Question

I just finished reading about scoping in the R intro, and am very curious about the <<- assignment.

The manual showed one (very interesting) examp

Answer 1

The <<- operator can also be useful for Reference Classes when writing Reference Methods. For example:

myRFclass <- setRefClass(Class = "RF",
                         fields = list(A = "numeric",
                                       B = "numeric",
                                       C = function() A + B))
myRFclass$methods(show = function() cat("A =", A, "B =", B, "C =",C))
myRFclass$methods(changeA = function() A <<- A*B) # note the <<-
obj1 <- myRFclass(A = 2, B = 3)
obj1
# A = 2 B = 3 C = 5
obj1$changeA()
obj1
# A = 6 B = 3 C = 9