S4 object system in R Programming - Mini Project: Build & Apply

Create and Use an S4 Class in R

📖 Scenario: You are working with a library system that needs to keep track of books. Each book has a title and a number of pages.

🎯 Goal: You will create an S4 class called Book with slots for title and pages. Then you will create an object of this class and display its details.

📋 What You'll Learn

Create an S4 class named Book with slots title (character) and pages (numeric).

Create a variable called my_book that is an object of class Book with title 'The Great Gatsby' and pages 180.

Write a method to show the book details using the show function.

Print the my_book object to display its details.

💡 Why This Matters

🌍 Real World

Libraries and bookstores use object systems to manage book information efficiently and consistently.

💼 Career

Understanding S4 classes is important for R programmers working in data science, bioinformatics, or any field requiring structured data management.

1

Define the S4 class Book

Create an S4 class called Book with slots title of type character and pages of type numeric using setClass.

R Programming

# Your code here

Need a hint?

Use setClass with slots = list(title = "character", pages = "numeric").

2

Create an object my_book of class Book

Create a variable called my_book that is a new object of class Book with title set to 'The Great Gatsby' and pages set to 180 using new.

R Programming

setClass("Book", slots = list(title = "character", pages = "numeric"))
# Your code here

Need a hint?

Use new("Book", title = "The Great Gatsby", pages = 180) to create the object.

3

Define a show method for Book

Define a show method for objects of class Book that prints the book's title and number of pages in a friendly message using setMethod.

R Programming

setClass("Book", slots = list(title = "character", pages = "numeric"))
my_book <- new("Book", title = "The Great Gatsby", pages = 180)
# Your code here

Need a hint?

Use setMethod("show", "Book", function(object) { ... }) and inside use cat to print the details.

4

Print the my_book object

Write a line of code to print the my_book object so that the show method runs and displays the book details.

R Programming

setClass("Book", slots = list(title = "character", pages = "numeric"))
my_book <- new("Book", title = "The Great Gatsby", pages = 180)
setMethod("show", "Book", function(object) {
  cat("Book Title:", object@title, "\nPages:", object@pages, "\n")
})
# Your code here

Need a hint?

Use print(my_book) to display the book details using the show method.