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R While Loops
Loops
Loops can create a code block as long as the specified condition is reached.
Loops work because they save time, reduce errors, and make the code more readable.
R has two loop commands:
whileloopsforloops
R While Loops
With a while loop we can make a set of statements as long as the condition is TRUE:
Example
Print i as long as i is less than 6:
while (i < 6) {
print(i)
i <- i + 1
}
In the example above, the loop will continue to generate numbers from 1 to 5. The loop will stop at 6 because 6 < 6 is FALSE.
The loop while it needs a variable that is right for you, in this example we need to define the variable variable, i, which we have set in 1.
Note: remember to increment i, otherwise the loop will continue permanently.
Break
With a break statement, we can stop the loop even if the situation says TRUE:
Example
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 end the loop using the break statement when i is equal to 4 (i == 4).
Next
With the next statement, we can skip repeats without breaking the loop:
Example
Skip the value of 3:
i <- 0
while (i < 6) {
i <- i + 1
if (i == 3) {
next
}
print(i)
}
If the loop exceeds 3 loops, it will skip and continue loop.
Yahtzee!
If .. Else Combined with a While Loop
To demonstrate a practical example, let us say we play a game of Yahtzee!
Example
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 exceeds the range from 1 to 5, it prints "No Yahtzee". Whenever it exceeds 6, it prints "Yahtzee!".