📊 Day 4: Grouped Bar Chart in Python 

🔍 What is a Grouped Bar Chart?

A grouped bar chart (also called a clustered bar chart) is used to compare multiple values within the same category.

Instead of one bar per category, you see multiple bars placed side by side for easy comparison.

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✅ When Should You Use a Grouped Bar Chart?

Use a grouped bar chart when:

• You have two or more sub-categories

• You want to compare values within and across categories

• Exact comparison between groups is important

Real-world examples:

• Sales of multiple products across years

• Marks of boys vs girls in each class

• Revenue comparison of companies per quarter

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📊 Example Dataset

Let’s compare sales of two products over different years:

Year	Product A	Product B
2022	50	40
2023	70	60
2024	90	75

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🧠 Python Code: Grouped Bar Chart Using Matplotlib

import matplotlib.pyplot as plt
import numpy as np

# Data
years = ['2022', '2023', '2024']
product_a = [50, 70, 90]
product_b = [40, 60, 75] 

# X positions
x = np.arange(len(years))
width = 0.35

# Create grouped bars
plt.bar(x - width/2, product_a, width, label='Product A')
plt.bar(x + width/2, product_b, width, label='Product B') 

# Labels and title
plt.xlabel('Year')
plt.ylabel('Sales')
plt.title('Yearly Sales Comparison')
plt.xticks(x, years)
plt.legend()

# Display chart 
plt.show()

🧩 Code Explanation (Simple)

• np.arange() → creates x-axis positions

• width → controls bar thickness and spacing

• x - width/2 & x + width/2 → place bars side by side

• legend() → explains which bar belongs to which category

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📊 Grouped Bar Chart vs Stacked Bar Chart

Grouped Bar Chart	Stacked Bar Chart
Bars are side-by-side	Bars are stacked
Easy comparison	Shows composition
Best for exact values	Best for proportions

🔑 Key Takeaways

✔ Used to compare multiple values per category
✔ Bars are placed side by side
✔ Ideal for detailed comparisons