While loop in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a while loop in R?

A while loop in R repeats a block of code as long as a given condition is TRUE. It checks the condition before each repetition.

beginner

How do you write a basic while loop in R?

Use the syntax:<br>

while(condition) {
  # code to repeat
}

<br>The code inside runs while the condition is TRUE.

beginner

What happens if the condition in a while loop is FALSE at the start?

The code inside the while loop does not run at all because the condition is checked before the first iteration.

intermediate

How can you avoid an infinite loop with a while loop?

Make sure the condition will eventually become FALSE by changing variables inside the loop. Otherwise, the loop runs forever.

beginner

Example: What does this R code print?<br>

i <- 1
while(i <= 3) {
  print(i)
  i <- i + 1
}

It prints:<br>1<br>2<br>3<br>Because i starts at 1 and increases by 1 each time until it is greater than 3.

What does a while loop do in R?

A Repeats code a fixed number of times

B Repeats code while a condition is TRUE

C Runs code once regardless of condition

D Stops the program immediately

A while loop repeats the code block as long as the condition remains TRUE.

When is the condition in a while loop checked?

A Only once at the start

B After each repetition

C Before each repetition

D Never

The condition is checked before each time the loop runs.

What happens if the while loop condition is FALSE at the start?

A The loop code does not run

B The loop runs once

C The loop runs infinitely

D The program crashes

If the condition is FALSE initially, the loop body is skipped.

How can you prevent an infinite while loop?

A Use a for loop instead

B Do nothing; infinite loops are normal

C Add a break statement outside the loop

D Change variables inside the loop to eventually make the condition FALSE

You must update variables so the condition becomes FALSE to stop the loop.

What will this code print?<br>i <- 2<br>while(i < 5) {<br> print(i)<br> i <- i + 2<br>}

A 2 and 4

B 2, 3, 4

C 2, 4, 6

D Nothing

It prints 2 and 4 because i increases by 2 each time and stops before 5.

Explain how a while loop works in R and give a simple example.

Think about how you repeat a task until something changes.

What is an infinite loop and how can you avoid it when using a while loop?

Imagine a clock that never stops ticking.