Accessing elements ([], [[]], $) in R Programming - Mini Project: Build & Apply

Accessing elements in R with [], [[]], and $

📖 Scenario: You are working with a list in R that stores information about a book. You want to learn how to access different parts of this list using three common methods: [], [[]], and $.

🎯 Goal: Build a simple R script that creates a list with book details, sets a variable for the key to access, extracts information using the three methods, and prints the results.

📋 What You'll Learn

Create a list named book with exact elements: title = "The Hobbit", author = "J.R.R. Tolkien", year = 1937

Create a variable named key and set it to "author"

Use book["title"] to access the title and store it in title_brackets

Use book[[key]] to access the author and store it in author_double_brackets

Use book$year to access the year and store it in year_dollar

Print the three variables in order: title_brackets, author_double_brackets, year_dollar

💡 Why This Matters

🌍 Real World

Lists in R are used to store related data like records, settings, or grouped information. Knowing how to access elements helps you work with data efficiently.

💼 Career

Data analysts and scientists often manipulate lists in R to extract and analyze data. Understanding these access methods is essential for data cleaning and preparation.

1

Create the book list

Create a list called book with these exact elements: title = "The Hobbit", author = "J.R.R. Tolkien", and year = 1937

R Programming

# Create the book list with title, author, and year
# Your code here

Need a hint?

Use the list() function with named elements for title, author, and year.

2

Create the key variable

Create a variable called key and set it to the string "author"

R Programming

book <- list(title = "The Hobbit", author = "J.R.R. Tolkien", year = 1937)
# Create the key variable with value "author"
# Your code here

Need a hint?

Assign the string "author" to the variable key.

3

Access elements using [], [[]], and $

Use book["title"] to get the title and save it in title_brackets. Use book[[key]] to get the author and save it in author_double_brackets. Use book$year to get the year and save it in year_dollar

R Programming

book <- list(title = "The Hobbit", author = "J.R.R. Tolkien", year = 1937)
key <- "author"
# Access title with book["title"] and save to title_brackets
# Access author with book[[key]] and save to author_double_brackets
# Access year with book$year and save to year_dollar
# Your code here

Need a hint?

Remember that book["title"] returns a list, book[[key]] returns the element itself, and book$year accesses the element by name.

4

Print the accessed elements

Print the variables title_brackets, author_double_brackets, and year_dollar in this order, each on its own line

R Programming

book <- list(title = "The Hobbit", author = "J.R.R. Tolkien", year = 1937)
key <- "author"
title_brackets <- book["title"]
author_double_brackets <- book[[key]]
year_dollar <- book$year
# Print title_brackets, author_double_brackets, and year_dollar each on a new line
# Your code here

Need a hint?

Use print() to show each variable on its own line.