Iterator Loop in R

An iterator is a special type of object that generalizes the notion of a looping variable. When passed as an argument to a function that knows what to do with it, the iterator supplies a sequence of values. The iterator also maintains information about its state, in particular its current index

# Simple

i1 <- iter(1:3)

 nextElem(i1)

[1] 1

 nextElem(i1)

[1] 2

 nextElem(i1)

[1] 3

 # vector iterator

i1 <- iter(1:3, checkFunc=function(i) i %% 2 == 0)

 nextElem(i1)

[1] 2

Note : For Iterator install-> library(iterators)