6.6 break/next to exit and skip interations

The break argument is used to exit a loop immediately, regardless of what iteration the loop may be on. break arguments are typically embedded in an if statement in which a condition is assessed, if TRUE break out of the loop, if FALSE continue on with the loop. In a nested looping situation, where there is a loop inside another loop, this statement exits from the innermost loop that is being evaluated.

In this example, the for loop will iterate for each element in x; however, when it gets to the element that equals 3 it will break out and end the for loop process.

x <- 1:5

for (i in x) {
        if (i == 3){
                break
                }
        print(i)
}
[1] 1
[1] 2

The next argument is useful when we want to skip the current iteration of a loop without terminating it. On encountering next, the R parser skips further evaluation and starts the next iteration of the loop. In this example, the for loop will iterate for each element in x; however, when it gets to the element that equals 3 it will skip the for loop execution of printing the element and simply jump to the next iteration.

x <- 1:5

for (i in x) {
        if (i == 3){
                next
                }
        print(i)
}
[1] 1
[1] 2
[1] 4
[1] 5