Scoping Fun in R

scoping.R

## In the end, what is the twelth column of 'dat', a, and b?
## why does the local() not matter in thirteen?
a <- 10
b <- 10
dat <- local(
  data.frame(
    first = b,
    second = a <- 0 -> b,
    third = a <- rnorm(10, mean = a),
    fourth = a / 2,
    fifth = a <- rnorm(10, mean = a <- b),
    sixth = a * rnorm(10, b) -> a,
    seventh = b <- a^2,
    eigth = {rm(b); 1:10},
    ninth = a * b,
    tenth = b <<- a -> b,
    eleventh = {rm(a); b <- 10:1}, twelth = a,
    thirteenth = local(a <<- b -> a)
  )
)