Apply functions on matrices in R Programming - Mini Project: Build & Apply

Apply functions on matrices

📖 Scenario: You work in a small bakery that tracks daily sales of different types of bread in a matrix. Each row represents a day, and each column represents a bread type.You want to analyze the sales data by applying functions to the matrix rows and columns.

🎯 Goal: Build an R program that creates a sales matrix, sets a threshold for good sales, applies functions to calculate total sales per day and average sales per bread type, and prints the results.

📋 What You'll Learn

Create a matrix called sales with 3 rows and 4 columns using the exact values: 10, 15, 20, 25, 5, 10, 15, 20, 0, 5, 10, 15

Create a variable called good_sales_threshold and set it to 15

Use apply() to calculate total sales per day (sum of each row) and store it in total_sales_per_day

Use apply() to calculate average sales per bread type (mean of each column) and store it in average_sales_per_bread

Print total_sales_per_day and average_sales_per_bread

💡 Why This Matters

🌍 Real World

Analyzing sales data in a bakery or any small business helps understand daily performance and product popularity.

💼 Career

Data analysts and business managers often use matrix operations and apply functions to summarize and interpret data efficiently.

1

Create the sales matrix

Create a matrix called sales with 3 rows and 4 columns using these exact values in this order: 10, 15, 20, 25, 5, 10, 15, 20, 0, 5, 10, 15

R Programming

# Create the sales matrix with the given values
# Your code here

Need a hint?

Use the matrix() function with byrow = TRUE to fill rows first.

2

Set the good sales threshold

Create a variable called good_sales_threshold and set it to 15

R Programming

sales <- matrix(c(10, 15, 20, 25, 5, 10, 15, 20, 0, 5, 10, 15), nrow = 3, ncol = 4, byrow = TRUE)
# Set the good sales threshold to 15
# Your code here

Need a hint?

Just assign the number 15 to the variable good_sales_threshold.

3

Calculate total sales per day and average sales per bread type

Use apply() on the sales matrix to calculate total sales per day (sum of each row) and store it in total_sales_per_day. Then use apply() to calculate average sales per bread type (mean of each column) and store it in average_sales_per_bread.

R Programming

sales <- matrix(c(10, 15, 20, 25, 5, 10, 15, 20, 0, 5, 10, 15), nrow = 3, ncol = 4, byrow = TRUE)
good_sales_threshold <- 15
# Calculate total sales per day using apply()
# Calculate average sales per bread type using apply()
# Your code here

Need a hint?

Use apply(sales, 1, sum) for rows and apply(sales, 2, mean) for columns.

4

Print the results

Print the variables total_sales_per_day and average_sales_per_bread using two separate print() statements.

R Programming

sales <- matrix(c(10, 15, 20, 25, 5, 10, 15, 20, 0, 5, 10, 15), nrow = 3, ncol = 4, byrow = TRUE)
good_sales_threshold <- 15
total_sales_per_day <- apply(sales, 1, sum)
average_sales_per_bread <- apply(sales, 2, mean)
# Print total_sales_per_day
# Print average_sales_per_bread
# Your code here

Need a hint?

Use print(total_sales_per_day) and print(average_sales_per_bread).