Big Data Analysis / Data Mining 2025-FA Quiz 3 (Oct 30, Period 4)

1. What will be the output of the following code? x <- 5 if (x > 10) { result <- "greater than 10" } else { result <- "less than or equal to 10" } print(result)

"greater than 10"

"less than or equal to 10"

Error: object 'result' not found

False

In the given code, the variable `x` is assigned the value 5. The conditional statement checks if `x` is greater than 10. Since 5 is not greater than 10, the code inside the `else` block is executed, assigning the string "less than or equal to 10" to the variable `result`. Finally, the `print(result)` function outputs the value of `result`, which is "less than or equal to 10". Thus, the output of the code is the string "less than or equal to 10".

Explanation

In the given code, the variable `x` is assigned the value 5. The conditional statement checks if `x` is greater than 10. Since 5 is not greater than 10, the code inside the `else` block is executed, assigning the string "less than or equal to 10" to the variable `result`. Finally, the `print(result)` function outputs the value of `result`, which is "less than or equal to 10". Thus, the output of the code is the string "less than or equal to 10".

2. What will be the output of the following R code snippet? vector <- c(3, 6, 9, 12) for (num in vector) { print(num * 2) }

6 12 18 24

3 6 9 12

3 6 9 12 6 12 18 24

6 12 18 24 3 6 9 12

The R code snippet defines a vector containing the values 3, 6, 9, and 12. It then uses a for loop to iterate through each element in the vector, multiplying each number by 2 and printing the result. Therefore, the output will be the doubled values of the original vector: 6, 12, 18, and 24, printed sequentially.

Explanation

The R code snippet defines a vector containing the values 3, 6, 9, and 12. It then uses a for loop to iterate through each element in the vector, multiplying each number by 2 and printing the result. Therefore, the output will be the doubled values of the original vector: 6, 12, 18, and 24, printed sequentially.

3. What is the output of the following for loop code snippet in R? vec <- c(3, 6, 9, 12) total <- 0 for (i in vec) { total <- total + i } print(total)

18

30

15

45

The for loop iterates over each element in the vector `vec`, which contains the values 3, 6, 9, and 12. During each iteration, the current value of `i` is added to the variable `total`, which starts at 0. The calculations are as follows: 0 + 3 = 3, 3 + 6 = 9, 9 + 9 = 18, and finally, 18 + 12 = 30. After all iterations, the final value of `total`, which is printed, is 30.

Explanation

The for loop iterates over each element in the vector `vec`, which contains the values 3, 6, 9, and 12. During each iteration, the current value of `i` is added to the variable `total`, which starts at 0. The calculations are as follows: 0 + 3 = 3, 3 + 6 = 9, 9 + 9 = 18, and finally, 18 + 12 = 30. After all iterations, the final value of `total`, which is printed, is 30.

4. What is the purpose of a while loop in R?

To execute a block of code a specific number of times

To iterate over a sequence of values

To repeat a block of code as long as a condition is true

To terminate the execution of a program

A while loop in R is designed to repeatedly execute a block of code as long as a specified condition evaluates to true. This allows for dynamic control over the execution flow, enabling the code to run an indefinite number of times until the condition changes. It is particularly useful for scenarios where the number of iterations is not known in advance, allowing for flexible and adaptive programming.

Explanation

A while loop in R is designed to repeatedly execute a block of code as long as a specified condition evaluates to true. This allows for dynamic control over the execution flow, enabling the code to run an indefinite number of times until the condition changes. It is particularly useful for scenarios where the number of iterations is not known in advance, allowing for flexible and adaptive programming.

5. What will be the output of the following R code snippet? x <- 1 while(x <= 5) { print(x) x <- x + 2 }

1 2 3 4 5

1 3 5

2 4

1

The R code initializes a variable `x` with the value 1 and enters a while loop that continues as long as `x` is less than or equal to 5. Inside the loop, it prints the current value of `x`, then increments `x` by 2. The loop will print 1, then 3, and finally 5 before `x` becomes 7, which exits the loop. Thus, the output of the code snippet is 1, 3, and 5.

Explanation

The R code initializes a variable `x` with the value 1 and enters a while loop that continues as long as `x` is less than or equal to 5. Inside the loop, it prints the current value of `x`, then increments `x` by 2. The loop will print 1, then 3, and finally 5 before `x` becomes 7, which exits the loop. Thus, the output of the code snippet is 1, 3, and 5.