Why operators drive computation in R Programming - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two numbers and print the result.

R Programming

result <- 5 [1] 3
print(result)

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

The plus operator + adds two numbers together.

2fill in blank

medium

Complete the code to multiply two numbers and print the result.

R Programming

result <- 4 [1] 7
print(result)

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

A/

B-

C+

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition or division instead of multiplication.

The asterisk * operator multiplies two numbers.

3fill in blank

hard

Fix the error in the code to divide two numbers and print the result.

R Programming

result <- 10 [1] 2
print(result)

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

A*

B+

C/

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication or subtraction instead of division.

The forward slash / operator divides the first number by the second.

4fill in blank

hard

Fill both blanks to create a named vector with names for the numbers 4 and 5.

R Programming

squares <- c([1] = 4, [2] = 5)
print(squares)

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

Afour

Bsix

Cfive

Dseven

Attempts:

3 left

💡 Hint

Common Mistakes

Using names that do not match the vector values.

The names four and five label the vector elements for 4 and 5.

5fill in blank

hard

Fill all three blanks to create a vector of numbers, filter those greater than 3, and square them.

R Programming

numbers <- c([1], [2], [3])
squares <- numbers[numbers > 3]^2
print(squares)

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

A2

B4

C5

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using only numbers less than or equal to 3.

The vector contains 2, 4, and 5. Only 4 and 5 are greater than 3 and get squared.

Practice

1. What is the main role of operators in R programming?

easy

A. To perform calculations and comparisons

B. To store data permanently

C. To create new variables automatically

D. To display messages on the screen

Solution

1. Step 1: Understand what operators do

   Operators are symbols or words that tell the computer how to calculate or compare values.

2. Step 2: Identify the correct role

   They do not store data or display messages but perform calculations and comparisons.

3. Final Answer:

   To perform calculations and comparisons -> Option A

4. Quick Check:

   Operators = calculations/comparisons [OK]

Hint: Operators always tell how to calculate or compare [OK]

Common Mistakes:

• Thinking operators store data
• Confusing operators with functions that display output
• Believing operators create variables automatically

2. Which of the following is the correct way to add two numbers in R?

easy

A. x <- 5 + 3

B. x <- 5 plus 3

C. x <- 5 & 3

D. x <- 5 == 3

Solution

1. Step 1: Identify the addition operator in R

   The plus sign (+) is used to add numbers in R.

2. Step 2: Check each option

   x <- 5 + 3 uses + correctly; x <- 5 & 3 uses logical AND; x <- 5 plus 3 uses invalid 'plus'; x <- 5 == 3 uses comparison.

3. Final Answer:

   x <- 5 + 3 -> Option A

4. Quick Check:

   Addition uses + operator [OK]

Hint: Use + for addition, not words or logical operators [OK]

Common Mistakes:

• Using words like 'plus' instead of +
• Confusing logical operators (&) with arithmetic
• Using comparison operator (==) instead of addition

3. What is the output of this R code?

x <- 10
y <- 4
z <- x %% y
print(z)

medium

A. 6

B. 0

C. 2

D. Error

Solution

1. Step 1: Understand the modulo operator %% in R

   The %% operator gives the remainder of division of x by y.

2. Step 2: Calculate 10 %% 4

   10 divided by 4 is 2 remainder 2, so 10 %% 4 equals 2.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   10 %% 4 = 2 [OK]

Hint: %% gives remainder after division [OK]

Common Mistakes:

• Confusing %% with division operator /
• Expecting quotient instead of remainder
• Thinking %% causes error

4. Identify the error in this R code snippet:

a <- 5
b <- 10
c <- a +* b
print(c)

medium

A. Missing parentheses around a and b

B. print() cannot display variables

C. Variables a and b are not defined

D. Using +* which is not a valid operator

Solution

1. Step 1: Check the operator used between a and b

   The code uses +* which is not a valid operator in R.

2. Step 2: Understand valid operators

   Valid arithmetic operators include +, -, *, / but not combined +*.

3. Final Answer:

   Using +* which is not a valid operator -> Option D

4. Quick Check:

   +* is invalid operator [OK]

Hint: Check operators carefully; combined symbols may be invalid [OK]

Common Mistakes:

• Assuming +* is multiplication
• Thinking parentheses fix operator errors
• Believing print() cannot show variables

5. You want to create a new variable result that is the sum of a and b only if a is greater than b. Which R expression correctly uses operators to do this?

hard

A. result <- a + b && a > b

B. result <- if (a > b) a + b else 0

C. result <- a > b + a + b

D. result <- a + b if a > b

Solution

1. Step 1: Understand conditional assignment in R

   Use if-else to assign value based on condition a > b.

2. Step 2: Check each option's syntax and logic

   result <- if (a > b) a + b else 0 correctly uses if (a > b) a + b else 0; others misuse operators or syntax.

3. Final Answer:

   result <- if (a > b) a + b else 0 -> Option B

4. Quick Check:

   Conditional assignment uses if-else [OK]

Hint: Use if (condition) true_value else false_value [OK]

Common Mistakes:

• Placing if after expression incorrectly
• Using logical AND (&&) instead of if-else
• Combining comparison and addition without parentheses