Operator precedence in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this R code involving arithmetic and logical operators?

Consider the following R code snippet. What will be printed when it runs?

R Programming

result <- 3 + 4 * 2 > 10
print(result)

A [1] FALSE

B [1] 11

C [1] TRUE

D [1] 14

💡 Hint

Remember that multiplication happens before addition, and comparison operators are evaluated last.

Multiplication (*) has higher precedence than addition (+), so 4 * 2 = 8. Then 3 + 8 = 11. Comparisons have lower precedence than arithmetic operators, so finally 11 > 10 is TRUE. Output: [1] TRUE.

❓ Predict Output

intermediate

What is the value of x after this R expression?

What is the value of x after running this code?

R Programming

x <- 5
x <- x ^ 2 %% 3
print(x)

A [1] 1

B [1] 4

C [1] 7

D [1] 2

💡 Hint

Remember that exponentiation (^) has higher precedence than modulo (%%).

First, x ^ 2 is 5 squared = 25. Then 25 %% 3 is the remainder of 25 divided by 3, which is 1.

❓ Predict Output

advanced

What does this R code print with mixed logical and arithmetic operators?

What is the output of this R code?

R Programming

a <- 2
b <- 3
result <- a + b > 4 & b < 5
print(result)

A [1] 5

B [1] FALSE

C [1] NA

D [1] TRUE

💡 Hint

Check operator precedence: arithmetic first, then comparison, then logical AND (&).

First, a + b = 5. Then 5 > 4 is TRUE. Also, b < 5 is TRUE. TRUE & TRUE is TRUE.

❓ Predict Output

advanced

What is the output of this R code with nested parentheses and operators?

What will this code print?

R Programming

x <- 4
result <- (x + 2) * (x - 1) / 2
print(result)

A [1] 6

B [1] 9

C [1] 8

D [1] 10

💡 Hint

Calculate inside parentheses first, then multiplication and division from left to right.

(4 + 2) = 6, (4 - 1) = 3, then 6 * 3 / 2. Since * and / have the same precedence and are left-associative, (6 * 3) / 2 = 18 / 2 = 9.

❓ Predict Output

expert

What is the output of this complex R expression with mixed operators?

What does this R code print?

R Programming

x <- 3
y <- 4
z <- 5
result <- x + y * z ^ 2 %% 7 - 1
print(result)

A [1] 4

B [1] 10

C [1] 14

D [1] 12

💡 Hint

Remember the order: exponentiation (^), modulo (%%), multiplication (*), addition (+), subtraction (-).

Precedence: ^ first (right-associative), so z ^ 2 = 25.

Then * and %% have the same precedence (left-associative), so (y * 25) %% 7 = 100 %% 7 = 2 (since 7*14=98, 100-98=2).

Then + and - (left-associative): x + 2 = 5, 5 - 1 = 4.

Practice

1. In R, which operator has the highest precedence among these: +, *, ^, -?

easy

A. Subtraction (-)

B. Multiplication (*)

C. Addition (+)

D. Exponentiation (^)

Solution

1. Step 1: Recall operator precedence rules in R

   Exponentiation (^) has higher precedence than multiplication, addition, and subtraction.

2. Step 2: Compare given operators

   Among +, *, ^, and -, ^ is evaluated first.

3. Final Answer:

   Exponentiation (^) -> Option D

4. Quick Check:

   ^ > * > +, - [OK]

Hint: Remember: powers before multiply, multiply before add [OK]

Common Mistakes:

• Thinking multiplication is higher than exponentiation
• Confusing addition and subtraction precedence
• Ignoring operator precedence order

2. Which of the following R expressions is syntactically correct and respects operator precedence?

easy

A. 3 + 4 ** 2

B. 3 + 4 * 2

C. 3 + (4 * ) 2

D. 3 + * 4 2

Solution

1. Step 1: Check each expression for syntax correctness

   3 + 4 * 2 is a valid expression: addition and multiplication with correct syntax. Options A, B, and C have syntax errors.

2. Step 2: Confirm operator precedence in 3 + 4 * 2

   Multiplication happens before addition, so 4 * 2 is evaluated first, then added to 3.

3. Final Answer:

   3 + 4 * 2 -> Option B

4. Quick Check:

   Valid syntax and precedence respected [OK]

Hint: Check for valid operator placement and parentheses [OK]

Common Mistakes:

• Using invalid operators like ** in R
• Misplacing operators causing syntax errors
• Incorrect parentheses usage

3. What is the output of this R code?

result <- 2 + 3 * 4 ^ 2
print(result)

medium

A. 50

B. 74

C. 200

D. 100

Solution

1. Step 1: Evaluate exponentiation first

   4 ^ 2 equals 16.

2. Step 2: Multiply then add

   Multiply 3 by 16 to get 48, then add 2: 2 + 48 = 50.

3. Step 3: Confirm the calculation

   2 + 3 * 4 ^ 2 = 2 + 3 * 16 = 2 + 48 = 50.

4. Final Answer:

   50 -> Option A

5. Quick Check:

   ^ then * then + = 50 [OK]

Hint: Calculate powers first, then multiply, then add [OK]

Common Mistakes:

• Adding before multiplying
• Ignoring exponentiation precedence
• Misreading the expression order

4. Identify the error in this R expression:

value <- 5 + 2 * (3 - 1

medium

A. Missing closing parenthesis

B. Incorrect operator usage

C. Multiplication should be addition

D. No error, expression is correct

Solution

1. Step 1: Check parentheses balance

   The expression has an opening parenthesis after 2 * but no closing parenthesis.

2. Step 2: Confirm syntax error due to missing parenthesis

   R requires matching parentheses; missing one causes syntax error.

3. Final Answer:

   Missing closing parenthesis -> Option A

4. Quick Check:

   Parentheses must be balanced [OK]

Hint: Count opening and closing parentheses carefully [OK]

Common Mistakes:

• Ignoring missing parentheses
• Assuming operators are wrong instead
• Not checking syntax errors first

5. Given the vector v <- c(1, 2, 3), what is the result of this expression in R?

result <- 10 / 2 * v + 1

Choose the correct output.

hard

A. [1] 6 7 8

B. [1] 11 12 13

C. [1] 6 11 16

D. [1] 5 10 15

Solution

1. Step 1: Evaluate division and multiplication first

   10 / 2 equals 5, then multiply by vector v: 5 * c(1,2,3) = c(5,10,15).

2. Step 2: Add 1 to each element

   Add 1 to each element: c(5,10,15) + 1 = c(6,11,16).

3. Final Answer:

   [1] 6 11 16 -> Option C

4. Quick Check:

   Division and multiplication before addition [OK]

Hint: Do division and multiplication before addition on vectors [OK]

Common Mistakes:

• Adding 1 before multiplication
• Ignoring vectorized operations
• Misordering division and multiplication