filter() for row selection in R Programming - Mini Project: Build & Apply

Filter Rows in a Data Frame Using filter()

📖 Scenario: You work in a small bookstore and have a list of books with their prices and stock. You want to find which books cost less than $20 to plan a sale.

🎯 Goal: Build a small R program that creates a data frame of books, sets a price limit, filters the books cheaper than that limit using filter(), and prints the filtered list.

📋 What You'll Learn

Create a data frame called books with columns title, price, and stock with exact values

Create a variable called max_price set to 20

Use dplyr::filter() with books and price < max_price to get cheaper books

Print the filtered data frame

💡 Why This Matters

🌍 Real World

Filtering data frames is a common task in data analysis to focus on relevant information, like finding affordable products or available stock.

💼 Career

Data analysts and scientists often use filtering to clean and prepare data before making reports or decisions.

1

Create the books data frame

Create a data frame called books with these exact entries:
title: "Book A", "Book B", "Book C", "Book D"
price: 15, 25, 10, 30
stock: 5, 2, 8, 1

R Programming

# Create the data frame books with columns title, price, and stock
# Your code here

Need a hint?

Use data.frame() with vectors for each column named title, price, and stock.

2

Set the maximum price limit

Create a variable called max_price and set it to 20

R Programming

books <- data.frame(
  title = c("Book A", "Book B", "Book C", "Book D"),
  price = c(15, 25, 10, 30),
  stock = c(5, 2, 8, 1)
)
# Create max_price variable and set to 20
# Your code here

Need a hint?

Just assign the number 20 to a variable named max_price.

3

Filter books cheaper than max_price

Use dplyr::filter() with books and the condition price < max_price to create a new data frame called cheap_books

R Programming

books <- data.frame(
  title = c("Book A", "Book B", "Book C", "Book D"),
  price = c(15, 25, 10, 30),
  stock = c(5, 2, 8, 1)
)
max_price <- 20
# Load dplyr and filter books with price less than max_price
# Your code here

Need a hint?

Remember to load dplyr with library(dplyr) before using filter().

4

Print the filtered books

Write a print() statement to display the cheap_books data frame

R Programming

library(dplyr)

books <- data.frame(
  title = c("Book A", "Book B", "Book C", "Book D"),
  price = c(15, 25, 10, 30),
  stock = c(5, 2, 8, 1)
)
max_price <- 20

cheap_books <- filter(books, price < max_price)
# Print the cheap_books data frame
# Your code here

Need a hint?

Use print(cheap_books) to show the filtered books.