R Language Tutorial => Environments and Functions

Example

Variables declared inside a function only exist (unless passed) inside that function.

x <- 1

foo <- function(x) {
    y <- 3
    z <- x + y
    return(z)
}

y

Error: object 'y' not found

Variables passed into a function and then reassigned are overwritten, but only inside the function.

foo <- function(x) {
    x <- 2
    y <- 3
    z <- x + y
    return(z)
}

foo(1)
x

5

1

Variables assigned in a higher environment than a function exist within that function, without being passed.

foo <- function() {
    y <- 3
    z <- x + y
    return(z)
}
    
foo()

4

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