Accessing elements ([], [[]], $) in R Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to access the first element of the vector v.

R Programming

v <- c(10, 20, 30)
first_element <- v[1]1

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

A{

B[[

C$

D[

Attempts:

3 left

💡 Hint

Common Mistakes

Using double brackets [[ ]] which are for lists or data frames.

Using $ which is for named list or data frame elements.

In R, single square brackets [] are used to access elements of a vector by index.

2fill in blank

medium

Complete the code to extract the first element from the list lst.

R Programming

lst <- list(a = 5, b = 10)
first_element <- lst[1]1

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

A[[

B{

C$

D[

Attempts:

3 left

💡 Hint

Common Mistakes

Using single brackets which return a list, not the element.

Using $ without the element name.

Double square brackets [[ ]] extract the element itself from a list, not a sublist.

3fill in blank

hard

Fix the error in the code to access the element named 'b' in the list lst.

R Programming

lst <- list(a = 5, b = 10)
value <- lst[1]b

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

A$

B[[b]]

C[b]

D[['b']]

Attempts:

3 left

💡 Hint

Common Mistakes

Using brackets with unquoted names which causes an error.

Using double brackets without quotes around the name.

The dollar sign $ is used to access named elements in a list by name without quotes.

4fill in blank

hard

Fill both blanks to create a named vector and access the element named 'second'.

R Programming

vec <- c(first = 1, second = 2, third = 3)
value <- vec[1]"second"[2]

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

A[

B[[

C]

Attempts:

3 left

💡 Hint

Common Mistakes

Using double brackets which are not valid for vectors.

Forgetting to close the brackets.

Single brackets [] with quotes access named elements in a vector and return a vector of length 1.

5fill in blank

hard

Complete the code to create a list with named elements and access the element named 'age'.

R Programming

person <- list(name = "Alice", age = 30, city = "NY")
age_value <- person[1]"age"

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

A[

B[[

C]

Attempts:

3 left

💡 Hint

Common Mistakes

Using single brackets which return a sublist, not the element.

Not quoting the name inside the brackets.

Use double brackets [[ ]] with quotes to extract the element itself from a list by name.