Operator precedence in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is operator precedence in R?

Operator precedence is the set of rules that determines the order in which different operators are evaluated in an expression.

beginner

Which operator has higher precedence: multiplication (*) or addition (+)?

Multiplication (*) has higher precedence than addition (+), so it is evaluated first.

beginner

How does parentheses affect operator precedence?

Parentheses change the order of evaluation by forcing the expression inside them to be evaluated first, regardless of normal precedence rules.

intermediate

What is the precedence order between logical AND (&&) and logical OR (||) in R?

Logical AND (&&) has higher precedence than logical OR (||), so && is evaluated before ||.

advanced

In the expression 3 + 4 * 2 / (1 - 5)^2^3, which operation is evaluated first?

The expression inside parentheses (1 - 5) is evaluated first, then exponentiation (^), then multiplication (*) and division (/), and finally addition (+).

In R, which operator is evaluated first in the expression 5 + 3 * 2?

A Depends on variable types

B Addition (+)

C Multiplication (*)

D Both at the same time

Multiplication (*) has higher precedence than addition (+), so 3 * 2 is evaluated first.

What does parentheses do in an expression like (2 + 3) * 4?

A They change the operator precedence to default

B They make the expression inside evaluated first

C They have no effect

D They delay evaluation until later

Parentheses force the expression inside to be evaluated first, so 2 + 3 is done before multiplication.

Which has higher precedence in R: logical AND (&&) or logical OR (||)?

A Logical OR (||)

B Depends on the expression

C They have equal precedence

D Logical AND (&&)

Logical AND (&&) has higher precedence than logical OR (||).

In the expression 2^3^2, which exponentiation is done first?

A 3^2 first

B 2^3 first

C Both at the same time

D Exponentiation is left to right

Exponentiation in R is right-associative, so 3^2 is evaluated first.

What is the result of 4 + 6 / 3 in R?

A 6

B 3.33

C 7

D 6 + 4 / 3

Division (/) has higher precedence, so 6 / 3 = 2, then 4 + 2 = 6.

Explain how operator precedence affects the evaluation of the expression 7 + 3 * 2 in R.

Think about which operation R does first without parentheses.

Describe how parentheses can change the result of an expression with mixed operators in R.

Consider how you can force R to do addition before multiplication.

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