If-else statements in R Programming - Mini Project: Build & Apply

If-else statements

📖 Scenario: You are helping a small shop owner decide if a product is affordable for customers based on its price.

🎯 Goal: Build a simple R program that uses if-else statements to check if a product price is affordable or expensive compared to a set budget.

📋 What You'll Learn

Create a variable with the product price

Create a variable with the budget limit

Use an if-else statement to compare the price with the budget

Print 'Affordable' if the price is less than or equal to the budget

Print 'Expensive' if the price is greater than the budget

💡 Why This Matters

🌍 Real World

Shop owners often need to check if product prices fit within customer budgets to decide promotions or discounts.

💼 Career

Understanding if-else statements is essential for programming logic used in data analysis, automation, and decision-making tasks.

1

Create the product price variable

Create a variable called price and set it to 120.

R Programming

# Create a variable called price and set it to 120
# Your code here

Hint

Use the assignment operator <- to assign the value 120 to price.

2

Create the budget variable

Create a variable called budget and set it to 100.

R Programming

price <- 120
# Create a variable called budget and set it to 100
# Your code here

Hint

Use the assignment operator <- to assign the value 100 to budget.

3

Write the if-else statement

Write an if-else statement that checks if price is less than or equal to budget. If yes, assign the string 'Affordable' to a variable called result. Otherwise, assign 'Expensive' to result.

R Programming

price <- 120
budget <- 100
# Write an if-else statement to set result based on price and budget
# Your code here

Hint

Use if (price <= budget) { ... } else { ... } to decide the value of result.

4

Print the result

Write a line to print the value of the variable result.

R Programming

price <- 120
budget <- 100
if (price <= budget) {
  result <- 'Affordable'
} else {
  result <- 'Expensive'
}
# Print the result variable
# Your code here

Hint

Use print(result) to show the result on the screen.

Practice

1. What does an if-else statement do in R?

easy

A. It chooses which code to run based on a condition.

B. It repeats code multiple times.

C. It stores data in a list.

D. It creates a new function.

Solution

1. Step 1: Understand the purpose of if-else

   An if-else statement checks a condition and runs code depending on whether the condition is TRUE or FALSE.

2. Step 2: Compare options with the definition

   Only It chooses which code to run based on a condition. describes choosing code based on a condition, which matches if-else behavior.

3. Final Answer:

   It chooses which code to run based on a condition. -> Option A

4. Quick Check:

   If-else chooses code path = D [OK]

Hint: If-else picks code based on TRUE or FALSE condition [OK]

Common Mistakes:

• Confusing if-else with loops
• Thinking if-else stores data
• Mixing if-else with function creation

2. Which of the following is the correct syntax for an if-else statement in R?

easy

A. if (x > 0) { print("Positive") } else { print("Non-positive") }

B. if x > 0 then print("Positive") else print("Non-positive")

C. if x > 0 { print("Positive") } else { print("Non-positive") }

D. if (x > 0) print "Positive" else print "Non-positive"

Solution

1. Step 1: Recall R if-else syntax

   In R, conditions go inside parentheses, and code blocks inside curly braces.

2. Step 2: Check each option

   if (x > 0) { print("Positive") } else { print("Non-positive") } uses parentheses and braces correctly. Options A, C, and D miss parentheses or braces or use wrong keywords.

3. Final Answer:

   if (x > 0) { print("Positive") } else { print("Non-positive") } -> Option A

4. Quick Check:

   Correct if-else syntax uses ( ) and { } = B [OK]

Hint: Use parentheses for condition and braces for code blocks [OK]

Common Mistakes:

• Omitting parentheses around condition
• Missing curly braces for code blocks
• Using 'then' keyword which R does not use

3. What is the output of this R code?

score <- 75
if (score >= 60) {
  print("Pass")
} else {
  print("Fail")
}

medium

A. "Fail"

B. "Pass"

C. Error

D. No output

Solution

1. Step 1: Evaluate the condition

   The variable score is 75. The condition checks if 75 >= 60, which is TRUE.

2. Step 2: Determine which block runs

   Since the condition is TRUE, the code inside the if block runs, printing "Pass".

3. Final Answer:

   "Pass" -> Option B

4. Quick Check:

   75 >= 60 is TRUE, so output is "Pass" [OK]

Hint: Check if condition is TRUE to pick output [OK]

Common Mistakes:

• Confusing >= with >
• Thinking else block runs when condition is TRUE
• Ignoring quotes in printed output

4. Find the error in this R code snippet:

num <- 10
if num > 5 {
  print("Greater")
} else {
  print("Smaller")
}

medium

A. Using else without if

B. Missing curly braces around print statements

C. Variable num is not defined

D. Missing parentheses around the condition in if statement

Solution

1. Step 1: Check if statement syntax

   In R, the condition in if must be inside parentheses. Here, it's written as if num > 5 without parentheses.

2. Step 2: Verify other parts

   Curly braces are present, else is correctly used, and num is defined as 10.

3. Final Answer:

   Missing parentheses around the condition in if statement -> Option D

4. Quick Check:

   If condition needs ( ) in R [OK]

Hint: Always put condition inside parentheses in if [OK]

Common Mistakes:

• Omitting parentheses around condition
• Confusing curly braces placement
• Thinking else can stand alone

5. You want to write an R program that prints "Even" if a number is divisible by 2, "Odd" if divisible by 3 but not 2, and "Other" otherwise. Which code correctly uses if-else statements?

hard

A. if (num %% 2 == 0) {
print("Odd")
} else {
if (num %% 3 == 0) {
print("Even")
} else {
print("Other")
}
}

B. if (num %% 3 == 0) {
print("Odd")
} else if (num %% 2 == 0) {
print("Even")
} else {
print("Other")
}

C. if (num %% 2 == 0) {
print("Even")
} else if (num %% 3 == 0) {
print("Odd")
} else {
print("Other")
}

D. if (num %% 2 == 0) {
print("Odd")
} else if (num %% 3 == 0) {
print("Even")
} else {
print("Other")
}

Solution

1. Step 1: Understand the conditions order

   Check divisibility by 2 first to print "Even". If not divisible by 2, check divisibility by 3 to print "Odd". Otherwise print "Other".

2. Step 2: Match code with logic

   if (num %% 2 == 0) { print("Even") } else if (num %% 3 == 0) { print("Odd") } else { print("Other") } checks num %% 2 == 0 first, then num %% 3 == 0, then else. This matches the requirement exactly.

3. Final Answer:

   if (num %% 2 == 0) { print("Even") } else if (num %% 3 == 0) { print("Odd") } else { print("Other") } -> Option C

4. Quick Check:

   Check 2 first, then 3, else other = A [OK]

Hint: Check conditions in correct priority order [OK]

Common Mistakes:

• Checking divisibility by 3 before 2
• Swapping print messages for even and odd
• Missing nested else for other cases