While loop in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 1 to 5 using a while loop.

R Programming

i <- 1
while (i [1] 5) {
  print(i)
  i <- i + 1
}

Drag options to blanks, or click blank then click option'

A>=

B<=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'i < 5' which stops the loop before printing 5.

Using 'i > 5' which never runs the loop.

The condition i <= 5 ensures the loop runs while i is 1 through 5.

2fill in blank

medium

Complete the code to stop the loop when x reaches 10.

R Programming

x <- 1
while (x [1] 10) {
  print(x)
  x <- x + 1
}

Drag options to blanks, or click blank then click option'

A<

B>=

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' which includes 10 and runs one extra time.

Using '>' which never runs the loop.

The condition x < 10 stops the loop before x becomes 10.

3fill in blank

hard

Fix the error in the loop condition to avoid an infinite loop.

R Programming

count <- 5
while (count [1] 0) {
  print(count)
  count <- count - 1
}

Drag options to blanks, or click blank then click option'

A<=

B<

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' causes the loop to never run.

Using '<=' causes an infinite loop.

The condition count > 0 ensures the loop stops when count reaches 0.

4fill in blank

hard

Fill both blanks to create a loop that prints even numbers from 2 to 10.

R Programming

num <- 2
while (num [1] 10) {
  print(num)
  num <- num [2] 2
}

Drag options to blanks, or click blank then click option'

A<=

B<

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes 10 from printing.

Using '-' decreases num causing an infinite loop.

The loop runs while num is less than or equal to 10, and num increases by 2 each time.

5fill in blank

hard

Fill all three blanks to create a loop that prints squares of numbers from 1 to 5.

R Programming

i <- 1
while (i [1] 5) {
  print(i [2] i)
  i <- i [3] 1
}

Drag options to blanks, or click blank then click option'

A<=

B*

C+

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes 5 from printing.

Using '+' instead of '*' prints double i, not square.

Using '-' decreases i causing infinite loop.

The loop runs while i is less than or equal to 5, prints i squared, and increases i by 1 each time.

Practice

1. What does a while loop do in R?

easy

A. Executes code only once

B. Repeats code a fixed number of times

C. Repeats code as long as a condition is TRUE

D. Stops the program immediately

Solution

1. Step 1: Understand the purpose of a while loop

   A while loop runs repeatedly while its condition remains TRUE.

2. Step 2: Compare options

   Only Repeats code as long as a condition is TRUE correctly describes this behavior; others describe different concepts.

3. Final Answer:

   Repeats code as long as a condition is TRUE -> Option C

4. Quick Check:

   while loop = repeat while TRUE [OK]

Hint: While loops run while condition is TRUE, not fixed times [OK]

Common Mistakes:

• Confusing while loop with for loop
• Thinking it runs only once
• Believing it stops the program

2. Which of the following is the correct syntax for a while loop in R?

easy

A. while (i <= 5) { print(i); i <- i + 1 }

B. while i <= 5 { print(i); i <- i + 1 }

C. while i <= 5: print(i); i <- i + 1

D. while (i <= 5) print(i) i <- i + 1

Solution

1. Step 1: Check R while loop syntax

   R requires parentheses around the condition and braces for the loop body.

2. Step 2: Validate each option

   Only while (i <= 5) { print(i); i <- i + 1 } uses correct parentheses and braces syntax.

3. Final Answer:

   while (i <= 5) { print(i); i <- i + 1 } -> Option A

4. Quick Check:

   Correct syntax uses parentheses and braces [OK]

Hint: Use parentheses for condition and braces for loop body [OK]

Common Mistakes:

• Omitting parentheses around condition
• Missing braces for multiple statements
• Using colon or wrong punctuation

3. What is the output of this R code?

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

medium

A. Error: object 'i' not found

B. [1] 1 [1] 2

C. [1] 3

D. [1] 1 [1] 2 [1] 3

Solution

1. Step 1: Trace the loop iterations

   i starts at 1, loop runs while i <= 3, printing i each time and increasing i by 1.

2. Step 2: List printed values

   Values printed are 1, then 2, then 3 before loop stops.

3. Final Answer:

   [1] 1 [1] 2 [1] 3 -> Option D

4. Quick Check:

   Prints 1, 2, 3 in order [OK]

Hint: Increment loop variable inside while to avoid infinite loop [OK]

Common Mistakes:

• Forgetting to increment i causing infinite loop
• Expecting only last value printed
• Confusing output format

4. Identify the error in this R while loop code:

i <- 1
while (i < 5) {
  print(i)
}

medium

A. Missing increment of i inside the loop

B. Incorrect condition syntax

C. print() function is invalid

D. Variable i is not initialized

Solution

1. Step 1: Analyze loop body

   The loop prints i but never changes i, so i stays 1 forever.

2. Step 2: Understand consequence

   Without increment, the condition i < 5 is always TRUE, causing infinite loop.

3. Final Answer:

   Missing increment of i inside the loop -> Option A

4. Quick Check:

   Update loop variable to stop loop [OK]

Hint: Always update loop variable inside while to avoid infinite loop [OK]

Common Mistakes:

• Forgetting to increment loop variable
• Assuming print causes increment
• Misreading condition syntax

5. How can you use a while loop in R to calculate the factorial of 5?
Choose the correct code snippet.

hard

A. n <- 5
fact <- 0
i <- 1
while (i < n) {
fact <- fact * i
i <- i + 1
}
fact

B. n <- 5
fact <- 1
i <- 1
while (i <= n) {
fact <- fact * i
i <- i + 1
}
fact

C. n <- 5
fact <- 1
while (n > 0) {
fact <- fact + n
n <- n - 1
}
fact

D. n <- 5
fact <- 1
while (fact <= n) {
fact <- fact * n
n <- n - 1
}
fact

Solution

1. Step 1: Understand factorial calculation

   Factorial multiplies numbers from 1 to n, so loop must multiply fact by i from 1 to n.

2. Step 2: Check each code snippet

   n <- 5 fact <- 1 i <- 1 while (i <= n) { fact <- fact * i i <- i + 1 } fact correctly initializes fact=1, loops i from 1 to n, multiplying fact by i each time.

3. Final Answer:

   n <- 5 fact <- 1 i <- 1 while (i <= n) { fact <- fact * i i <- i + 1 } fact -> Option B

4. Quick Check:

   Multiply 1 to 5 sequentially for factorial [OK]

Hint: Multiply from 1 to n inside while loop for factorial [OK]

Common Mistakes:

• Using addition instead of multiplication
• Incorrect loop condition
• Starting fact at 0 causing zero result