How to Create Histogram in Matplotlib: Simple Guide

To create a histogram in matplotlib, use the plt.hist() function with your data array as input. This function automatically groups data into bins and displays the frequency distribution as bars.

Syntax

The basic syntax for creating a histogram in Matplotlib is:

• plt.hist(data, bins, color, alpha)

where:

• data is the list or array of numeric values.
• bins controls how many groups (bars) the data is split into.
• color sets the color of the bars.
• alpha controls the transparency of the bars (0 to 1).

python

import matplotlib.pyplot as plt

plt.hist(data, bins=10, color='blue', alpha=0.7)
plt.show()

Example

This example shows how to create a histogram of 100 random numbers between 0 and 50, split into 10 bins. It demonstrates how the data is grouped and displayed as bars.

python

import matplotlib.pyplot as plt
import numpy as np

# Generate 100 random numbers from 0 to 50
data = np.random.randint(0, 51, 100)

# Create histogram with 10 bins
plt.hist(data, bins=10, color='green', alpha=0.6)
plt.title('Histogram of Random Numbers')
plt.xlabel('Value Range')
plt.ylabel('Frequency')
plt.show()

Output

A histogram plot window showing 10 green bars representing frequency counts of random numbers in each range.

Common Pitfalls

Common mistakes when creating histograms include:

• Not specifying bins, which can lead to too few or too many bars.
• Passing non-numeric data, causing errors.
• Forgetting to call plt.show() to display the plot.
• Using inappropriate transparency or colors that make bars hard to see.

Example of a wrong and right way:

python

# Wrong: No bins specified, default may not suit data
plt.hist(data)
plt.show()

# Right: Specify bins for clearer grouping
plt.hist(data, bins=15)
plt.show()

Quick Reference

Here is a quick reference for plt.hist() parameters:

Parameter	Description	Example
data	Numeric data array to plot	[1, 2, 3, 4, 5]
bins	Number of bars or bin edges	10 or [0,5,10,15]
color	Bar color	'blue', '#FF5733'
alpha	Transparency level (0 to 1)	0.5
edgecolor	Color of bar edges	'black'
density	Normalize histogram to form a probability density	True or False

Key Takeaways

Use plt.hist() with your numeric data to create a histogram easily.

Specify bins to control how data groups into bars for better clarity.

Always call plt.show() to display the histogram plot.

Avoid non-numeric data and choose colors and transparency for clear visuals.

Use parameters like edgecolor and density to customize the histogram appearance.