List creation in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a list with numbers 1 to 5.

R Programming

my_list <- [1](1, 2, 3, 4, 5)

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

Aarray

Bc

Cvector

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using list() creates a list but not a simple vector of numbers.

Using vector() requires specifying the type and length.

The c() function combines values into a vector or list in R.

2fill in blank

medium

Complete the code to create a list with elements 'apple', 'banana', and 'cherry'.

R Programming

fruits <- [1]("apple", "banana", "cherry")

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

Alist

Barray

Cvector

Dc

Attempts:

3 left

💡 Hint

Common Mistakes

Using list() creates a list but the question expects a vector.

Using vector() requires specifying the type and length.

The c() function combines character elements into a vector.

3fill in blank

hard

Fix the error in the code to create a list with numbers 1, 2, and 3.

R Programming

numbers <- [1](1, 2, 3)

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

Ac

Blist

Cvector

Darray

Attempts:

3 left

💡 Hint

Common Mistakes

Missing commas between elements causes syntax errors.

Using list() is valid but the question asks to fix the error in this code.

The elements must be separated by commas inside c().

4fill in blank

hard

Fill both blanks to create a list of numbers from 1 to 5 and check its length.

R Programming

my_list <- [1](1, 2, 3, 4, 5)
length_of_list <- [2](my_list)

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

Ac

Blength

Clist

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using list() instead of c() changes the data structure.

Using size() is not a valid function in R.

c() creates the vector and length() returns its length.

5fill in blank

hard

Fill all three blanks to create a list of fruits, access the second fruit, and get the total count.

R Programming

fruits <- [1]("apple", "banana", "cherry")
second_fruit <- fruits[[2]]
total_fruits <- [3](fruits)

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

Ac

B2

Clength

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 2 to access the second fruit.

Using list() instead of c() changes the data type.

Using size() instead of length().

c() creates the vector, indexing with [2] gets the second fruit, and length() returns the count.

Practice

1. What is the correct way to create an empty list in R?

easy

A. my_list <- []

B. my_list <- list()

C. my_list <- {}

D. my_list <- array()

Solution

1. Step 1: Understand list creation in R

   In R, lists are created using the list() function.

2. Step 2: Identify the correct syntax

   The syntax my_list <- list() creates an empty list. Other options use incorrect syntax for lists.

3. Final Answer:

   my_list <- list() -> Option B

4. Quick Check:

   list() creates an empty list [OK]

Hint: Use list() to create lists in R [OK]

Common Mistakes:

• Using [] which is for vectors, not lists
• Using {} which is for expressions or sets in other languages
• Using array() which creates arrays, not lists

2. Which of the following is the correct syntax to add an element to the end of an existing list my_list in R?

easy

A. my_list[length(my_list) + 1] <- 5

B. my_list[length(my_list)] <- 5

C. my_list[[length(my_list) + 1]] <- 5

D. my_list[[length(my_list)]] <- 5

Solution

1. Step 1: Understand list indexing in R

   Lists in R use double brackets [[ ]] to access or assign elements.

2. Step 2: Add element at new position

   To add an element at the end, assign to my_list[[length(my_list) + 1]]. Single brackets return sublists, not elements.

3. Final Answer:

   my_list[[length(my_list) + 1]] <- 5 -> Option C

4. Quick Check:

   Use double brackets [[ ]] to add list elements [OK]

Hint: Use [[ ]] with length+1 to add list elements [OK]

Common Mistakes:

• Using single brackets [] which return sublists
• Assigning to existing last element index instead of length+1
• Confusing vector indexing with list indexing

3. What is the output of the following R code?

my_list <- list(10, "apple", TRUE)
my_list[[length(my_list) + 1]] <- 3.14
my_list

medium

A. list(10, "apple", TRUE, 3.14)

B. list(10, "apple", TRUE)

C. list(10, "apple", TRUE, list(3.14))

D. Error: cannot add element

Solution

1. Step 1: Initial list creation

   The list my_list starts with three elements: 10, "apple", and TRUE.

2. Step 2: Adding new element at the end

   Using my_list[[length(my_list) + 1]] <- 3.14 adds 3.14 as the fourth element.

3. Final Answer:

   list(10, "apple", TRUE, 3.14) -> Option A

4. Quick Check:

   Adding element extends list length by 1 [OK]

Hint: Adding with [[length+1]] appends element [OK]

Common Mistakes:

• Expecting no change to list
• Thinking new element is nested list
• Confusing single and double brackets

4. Identify the error in the following R code that tries to add an element to a list:

my_list <- list(1, 2, 3)
my_list[length(my_list) + 1] <- 4

medium

A. Using single brackets [] instead of double brackets [[ ]] for list element assignment

B. Using length(my_list) + 1 instead of length(my_list)

C. Assigning a number instead of a list

D. No error, code works fine

Solution

1. Step 1: Understand list element assignment

   In R, list elements must be assigned with double brackets [[ ]] to assign the element itself.

2. Step 2: Identify the mistake

   The code uses single brackets [] which assign a sublist, causing unexpected behavior or errors.

3. Final Answer:

   Using single brackets [] instead of double brackets [[ ]] for list element assignment -> Option A

4. Quick Check:

   Use [[ ]] to assign list elements [OK]

Hint: Use [[ ]] to assign list elements, not [ ] [OK]

Common Mistakes:

• Using [] which returns sublists, not elements
• Thinking length+1 is wrong index
• Assuming assigning number is invalid

5. You want to create a list in R that contains a number, a character vector, and another list. Which code correctly creates this list?

hard

A. my_list <- list(42, list("a", "b"), list(TRUE, FALSE))

B. my_list <- list(42, ["a", "b"], list(TRUE, FALSE))

C. my_list <- list(42, c("a", "b"), [TRUE, FALSE])

D. my_list <- list(42, c("a", "b"), list(TRUE, FALSE))

Solution

1. Step 1: Understand list elements types

   The list should contain a number, a character vector, and a nested list.

2. Step 2: Check syntax for each element

   Character vectors use c(), lists use list(). Square brackets [] are invalid in R for these purposes.

3. Step 3: Verify correct code

   my_list <- list(42, c("a", "b"), list(TRUE, FALSE)) correctly uses list(42, c("a", "b"), list(TRUE, FALSE)).

4. Final Answer:

   my_list <- list(42, c("a", "b"), list(TRUE, FALSE)) -> Option D

5. Quick Check:

   Use c() for vectors, list() for nested lists [OK]

Hint: Use c() for vectors and list() for nested lists [OK]

Common Mistakes:

• Using square brackets [] which are invalid in R
• Confusing vectors and lists syntax
• Not nesting lists properly