R While Loop

Loops

Loops can execute a block of code as long as a specified condition is reached.

Loops are handy because they save time, reduce errors, and they make code more readable.

R has two loop commands:

With the while loop we can execute a set of statements as long as a condition is TRUE:

Print i as long as i is less than 6:

i <- 1
while (i < 6) {
print(i)
i <- i + 1
}

In the example above, the loop will continue to produce numbers ranging from 1 to 5. The loop will stop at 6 because 6 < 6 is FALSE.

The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, i, which we set to 1.

Note: remember to increment i, or else the loop will continue forever.

With the break statement, we can stop the loop even if the while condition is TRUE:

Exit the loop if i is equal to 4.

i <- 1
while (i < 6) {
print(i)
i <- i + 1
if (i == 4) {
break
}
}

The loop will stop at 3 because we have chosen to finish the loop by using the break statement when i is equal to 4 (i == 4).

With the next statement, we can skip an iteration without terminating the loop:

Skip the value of 3:

i <- 0
while (i < 6) {
i <- i + 1
if (i == 3) {
next
}
print(i)
}

When the loop passes the value 3, it will skip it and continue to loop.

To demonstrate a practical example, let us say we play a game of Yahtzee!

Print "Yahtzee!" If the dice number is 6:

dice <- 1
while (dice <= 6) {
if (dice < 6) {
print("No Yahtzee")
} else {
print("Yahtzee!")
}
dice <- dice + 1
}

If the loop passes the values ranging from 1 to 5, it prints "No Yahtzee". Whenever it passes the value 6, it prints "Yahtzee!".