Bar Charts

A bar chart is one of the most common and intuitive ways to visualize data - using rectangular bars to represent and compare values across different categories, with the bar length proportional to the value it represents.

When to Use a Bar Chart

Bar charts work best when comparing a categorical variable against a numeric one - for example, comparing sales across different regions, or the number of students enrolled in different courses.

Vertical vs Horizontal Bar Charts

Vertical bar charts (column charts) are the most common, while horizontal bar charts are often preferred when category names are long, or when there are many categories to display, since they're easier to read top to bottom.

Plotting in Python

import matplotlib.pyplot as plt

categories = ["North", "South", "East", "West"]
sales = [250, 180, 300, 210]

plt.bar(categories, sales, color="steelblue")
plt.xlabel("Region")
plt.ylabel("Sales")
plt.title("Sales by Region")
plt.show()

Grouped and Stacked Bar Charts

When comparing multiple sub-categories at once, grouped bar charts place bars side by side, while stacked bar charts stack them on top of each other to also show the total across sub-categories.

Always start the y-axis at zero for bar charts - truncating the axis can visually exaggerate small differences between bars and mislead the viewer.

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