List creation in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested list creation

What is the output of this R code that creates a nested list?

R Programming

my_list <- list(a = 1:3, b = list(x = 10, y = 20))
str(my_list)

A

List of 3
 $ a: int 1
 $ b: int 2
 $ x: int 10

B

[1] 1 2 3
[1] 10 20

C

List of 2
 $ a: int [1:3] 1 2 3
 $ b:List of 2
  ..$ x: num 10
  ..$ y: num 20

D Error in list(a = 1:3, b = list(x = 10, y = 20)) : object not found

💡 Hint

Remember that list() can contain other lists as elements.

The code creates a list with two elements: 'a' is a vector of integers 1 to 3, and 'b' is another list with elements 'x' and 'y'. Printing shows the structure with nested lists.

🧠 Conceptual

intermediate

Understanding list element types

Which statement about lists in R is true?

A Lists can contain elements of different types, including other lists.

B Lists can only contain elements of the same type, like vectors.

C Lists are immutable and cannot be changed after creation.

D Lists automatically convert all elements to characters.

💡 Hint

Think about what you can store inside a list in R.

Lists in R are flexible containers that can hold elements of different types, including numbers, strings, vectors, and even other lists.

🔧 Debug

advanced

Identify the error in list creation

What error does this R code produce?

R Programming

my_list <- list(1, 2, 3
print(my_list)

A No error, prints list with elements 1, 2, 3

B Error: unexpected end of input

C Error: object 'my_list' not found

D Error: unexpected symbol in 'print(my_list)'

💡 Hint

Check if all parentheses are closed properly.

The code is missing a closing parenthesis for the list() function, causing an unexpected end of input error.

❓ Predict Output

advanced

Output of list element modification

What is the output after modifying a list element in R?

R Programming

my_list <- list(a = 5, b = 10)
my_list$a <- my_list$a + 3
print(my_list$a)

A [1] 8

B [1] 5

C Error: object 'a' not found

D [1] 10

💡 Hint

Look at how the element 'a' is changed by adding 3.

The element 'a' initially is 5, adding 3 makes it 8, so printing my_list$a outputs 8.

📝 Syntax

expert

Correct syntax for creating a list with named and unnamed elements

Which option correctly creates a list with one named element 'x' and two unnamed elements 10 and 20?

A list(x = 10, 20, 5)

B list(5, x = 10, 20)

C list(10, 20, x = 5)

D list(x = 5, 10, 20)

💡 Hint

Named elements can appear anywhere, unnamed elements keep their order.

Option D creates a list with named element 'x' = 5, followed by unnamed elements 10 and 20. This is valid syntax.