Highlight and annotate pattern in Matplotlib - Mini Project: Build & Apply

Highlight and Annotate Pattern

📖 Scenario: You are analyzing sales data for a small store. You want to see the sales trend over a week and highlight the day with the highest sales. This will help you understand when the store performs best.

🎯 Goal: Create a line chart of daily sales. Highlight the day with the highest sales using a different color and add an annotation to show the exact sales value on that day.

📋 What You'll Learn

Create a list called days with the days of the week.

Create a list called sales with the sales numbers for each day.

Find the day with the highest sales and store its index in max_index.

Plot the sales data as a line chart using matplotlib.

Highlight the highest sales day with a red dot.

Add an annotation showing the sales value on the highest sales day.

💡 Why This Matters

🌍 Real World

Highlighting important points in data charts helps businesses quickly see key information like best sales days.

💼 Career

Data analysts and scientists often highlight and annotate charts to communicate insights clearly to teams and managers.

1

Create sales data

Create a list called days with these exact values: 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'. Create another list called sales with these exact values: 150, 200, 170, 220, 180, 300, 250.

Matplotlib

# Create the days list and sales list
# Your code here

Need a hint?

Use square brackets to create lists. Put the days as strings in days and numbers in sales.

2

Find the highest sales day index

Create a variable called max_index and set it to the index of the highest value in the sales list using the sales.index() method and the max() function.

Matplotlib

days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
sales = [150, 200, 170, 220, 180, 300, 250]
# Find the index of the highest sales day
# Your code here

Need a hint?

Use max(sales) to get the highest sales number, then find its position with sales.index().

3

Plot sales and highlight highest day

Import matplotlib.pyplot as plt. Plot the sales data as a line chart using plt.plot(days, sales). Highlight the highest sales day by plotting a red dot at days[max_index] and sales[max_index] using plt.scatter() with color 'red' and size 100. Add an annotation with plt.annotate() showing the sales value at the highest sales day. Use the text f'Highest: {sales[max_index]}', position the text slightly above the red dot with xytext=(0,10) and textcoords='offset points'.

Matplotlib

days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
sales = [150, 200, 170, 220, 180, 300, 250]
max_index = sales.index(max(sales))

# Import matplotlib and plot the sales line chart
# Highlight the highest sales day with a red dot
# Add an annotation for the highest sales
# Your code here

Need a hint?

Use plt.plot() for the line, plt.scatter() for the red dot, and plt.annotate() to add text above the dot.

4

Show the plot

Add plt.show() to display the plot with the highlighted highest sales day and annotation.

Matplotlib

import matplotlib.pyplot as plt

days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
sales = [150, 200, 170, 220, 180, 300, 250]
max_index = sales.index(max(sales))

plt.plot(days, sales)
plt.scatter(days[max_index], sales[max_index], color='red', s=100)
plt.annotate(f'Highest: {sales[max_index]}', (days[max_index], sales[max_index]), xytext=(0,10), textcoords='offset points')
# Show the plot
# Your code here

Need a hint?

Use plt.show() to display the chart window.