while loop
In R programming, while loops are used to loop until a specific condition is met.
Syntax of while
loop
while (test_expression) {
statement
}
Here, test_expression
is evaluated and the body of the loop is entered if the result is TRUE
. The statements inside the loop are executed and the flow returns to evaluate the test_expression
again. This is repeated each time until test_expression
evaluates to FALSE
, in which case, the loop exits.
Flowchart of while
loop
Example of while
loop
i <- 1
while (i < 6) {
print(i)
i = i+1
}
Output
[1] 1 [1] 2 [1] 3 [1] 4 [1] 5
In the above example, i
is initialized to 1. Here, the test_expression
is i < 6
which evaluates to TRUE
since 1 is less than 6. So, the body of the loop is entered and i
is printed and incremented. Incrementing i
is important as this will eventually meet the exit condition. Failing to do so will result into an infinite loop. In the next iteration, the value of i
is 2 and the loop continues. This will continue until i
takes the value 6. The condition 6 < 6
will give FALSE
and the loop finally exits.