How to Create Horizontal Bar Chart in Matplotlib Easily

To create a horizontal bar chart in matplotlib, use the barh() function, which plots bars horizontally. You provide the positions on the y-axis and the bar lengths as arguments to barh().

Syntax

The basic syntax for creating a horizontal bar chart is:

• plt.barh(y_positions, bar_lengths, **options)

Here, y_positions is a list or array of positions on the y-axis where bars will be placed, and bar_lengths is the list or array of values that determine the length of each bar horizontally.

You can add optional parameters like color, height (thickness of bars), and tick_label (labels for each bar).

python

plt.barh(y_positions, bar_lengths, color='blue', height=0.5, tick_label=labels)

Example

This example shows how to create a simple horizontal bar chart with labeled bars and custom colors.

python

import matplotlib.pyplot as plt

labels = ['Apples', 'Bananas', 'Cherries', 'Dates']
values = [10, 15, 7, 12]
y_positions = range(len(labels))

plt.barh(y_positions, values, color='skyblue', height=0.6, tick_label=labels)
plt.xlabel('Quantity')
plt.title('Fruit Quantity')
plt.show()

Output

A horizontal bar chart with four bars labeled Apples, Bananas, Cherries, and Dates on the y-axis and their quantities on the x-axis.

Common Pitfalls

• Mixing up bar() and barh(): bar() creates vertical bars, while barh() creates horizontal bars.
• Not matching the length of y_positions and bar_lengths causes errors.
• Forgetting to set tick_label results in unlabeled bars, which can confuse viewers.
• Using incorrect axis labels can mislead interpretation.

python

import matplotlib.pyplot as plt

# Wrong: Using bar() for horizontal bars
labels = ['A', 'B', 'C']
values = [5, 7, 3]
plt.bar(labels, values)  # This creates vertical bars
plt.show()

# Right: Using barh() for horizontal bars
plt.barh(labels, values)
plt.show()

Output

First plot: vertical bars labeled A, B, C with heights 5, 7, 3.
Second plot: horizontal bars labeled A, B, C with lengths 5, 7, 3.

Quick Reference

Here is a quick summary of key parameters for plt.barh():

Parameter	Description
y_positions	Positions of bars on the y-axis (list or array)
bar_lengths	Lengths of each horizontal bar (list or array)
color	Color of the bars (string or list)
height	Thickness of each bar (float, default 0.8)
tick_label	Labels for each bar on y-axis (list)
align	'center' or 'edge' alignment of bars

Key Takeaways

Use plt.barh() to create horizontal bar charts in matplotlib.

Provide y-axis positions and bar lengths as the first two arguments.

Set tick_label to add labels to each bar for clarity.

Avoid mixing bar() and barh() to prevent confusion.

Customize colors and bar thickness with color and height parameters.