R

Question 1

is the built-in R constant that represents a missing value in datasets.

Answer 1

NA (or NA)

Question 2

is R’s primary data structure for tabular data, consisting of a list of equal-length vectors.

Answer 2

Data frame (or data.frame)

Question 3

is the operator used for matrix multiplication in R.

Answer 3

%*%

Question 4

is the R function used to determine the internal storage type of an object.

Answer 4

typeof()

Question 5

Is the R6 class operation that removes and returns the top item from a stack ADT.

Answer 5

pop (or pop())

Question 6

R is a compiled language that requires code to be translated into machine code before execution.
True or False

Answer 6

FALSE — R is an interpreted language (underline “compiled”)

Question 7

In R, variable names can start with a number or an underscore.
True or False

Answer 7

FALSE — Variable names cannot start with a number or underscore (underline “can”)

Question 8

The next statement in R skips the current iteration of a loop and proceeds to the next iteration.
True or False

Answer 8

TRUE

Question 9

R uses lexical scoping, meaning variables are looked up based on how functions are nested in the code.
True or False

Answer 9

TRUE

Question 10

The double square brackets [[]] are used for subsetting vectors and returning multiple elements.
True or False

R

Answer 10

FALSE — Double square brackets [[]] extract single elements from lists (underline “multiple”)

Question 11

Write an R function named calculate_bmi() that:
* Accepts two parameters: weight_kg (numeric) and height_cm (numeric)
* Calculates BMI using the formula: BMI = weight_kg / (height_m)^2, where height_m = height_cm/100
* Returns the BMI value rounded to 2 decimal places
* Includes a default value of 70 for weight_kg and 175 for height_cm

R

Answer 11

calculate_bmi <- function(weight_kg = 70, height_cm = 175) {
height_m <- height_cm / 100
bmi <- weight_kg / (height_m^2)
return(round(bmi, 2))
}

Question 12

Analyze the following R code and determine what will be printed:

x <- c(TRUE, FALSE, TRUE, FALSE)
y <- c(TRUE, TRUE, FALSE, FALSE)
result <- x & y
print(result)

R

Answer 12

TRUE FALSE FALSE FALSE

Explanation:
The & operator performs element-wise logical AND:
TRUE & TRUE = TRUE
FALSE & TRUE = FALSE
TRUE & FALSE = FALSE
FALSE & FALSE = FALSE

Question 13

Write a for loop that calculates the sum of all even numbers from 1 to 20 and prints the final sum.

R

Answer 13

sum_even <- 0
for (i in 1:20) {
    if (i %% 2 == 0) {
          sum_even <- sum_even + i
   }
}
print(paste("Sum of even numbers from 1 to 20:", sum_even))

Alternative answer:
sum_even <- sum(seq(2, 20, 2))
print(paste("Sum of even numbers from 1 to 20:", sum_even))

Question 14

Given the following data frame:

 students <- data.frame(
       id = 1:5,
       name = c("Ana", "Ben", "Carla", "David", "Elena"),
       score = c(92, 67, 78, 45, 88),
       stringsAsFactors = FALSE
)

Write R code to:
* Add a new column named status
* Assign “Pass” if score is ≥ 75, otherwise assign “Fail”
* Display only the name, score, and status columns for students who passed

R

Answer 14

students$status <- ifelse(students$score >= 75, "Pass", "Fail")
students[students$status == "Pass", c("name", "score", "status")]

OUTPUT:
name score status
1 Ana 92 Pass
3 Carla 78 Pass
5 Elena 88 Pass

Question 15

Write a recursive function named factorial() that calculates the factorial of a non-negative integer n (n! = n × (n-1) × … × 1). Test your function with n = 6.

R

Answer 15

factorial <- function(n) {
if (n <= 1) {
return(1)
} else {
return(n * factorial(n - 1))
}
}

result <- factorial(6)
print(paste(“Factorial of 6 is:”, result))

Factorial of 6 is: 720