What is the difference between assign() and

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Thomas Lumley answers this in a superb post on r-help the other day. <<- is about the enclosing environment so you can do thing like this (and again, I quote his post from April 22 in this thread):

make.accumulator<-function(){
    a <- 0
    function(x) {
        a <<- a + x
        a
    }
}

> f<-make.accumulator()
> f(1)
[1] 1
> f(1)
[1] 2
> f(11)
[1] 13
> f(11)
[1] 24

This is a legitimate use of <<- as “super-assignment” with lexical scope. And not simply to assign in the global environment. For that, Thomas has these choice words:

The Evil and Wrong use is to modify
variables in the global environment.

Very good advice.

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