Create Histograms with Matplotlib

Introduction

In this tutorial, we will learn how to create a histogram using Matplotlib library. A histogram is a graphical representation of the distribution of a dataset. It is an estimate of the probability distribution of a continuous variable. To create a histogram, we need to split the entire range of values into a series of intervals or bins, and then count how many values fall into each interval.

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Import the necessary libraries

First, we need to import the necessary libraries, which are NumPy and Matplotlib.

import matplotlib.pyplot as plt
import numpy as np

Generate random data

We will generate two sets of random data using NumPy's random.normal function. These sets will be used to create histograms with different styles.

np.random.seed(19680801)

mu_x = 200
sigma_x = 25
x = np.random.normal(mu_x, sigma_x, size=100)

mu_w = 200
sigma_w = 10
w = np.random.normal(mu_w, sigma_w, size=100)

Create a basic histogram

We will create a basic histogram using the hist function from Matplotlib. This histogram will have 10 equally sized bins.

plt.hist(x, bins=10)
plt.show()

Change the number of bins

We can change the number of bins by specifying the bins parameter in the hist function. In this example, we will create a histogram with 20 bins.

plt.hist(x, bins=20)
plt.show()

Change the histogram style

We can change the style of the histogram by specifying the histtype parameter in the hist function. In this example, we will create a histogram with a step curve that has a color fill.

plt.hist(x, bins=20, density=True, histtype='stepfilled', facecolor='g', alpha=0.75)
plt.show()

Create a histogram with custom bin widths

We can create a histogram with custom and unequal bin widths by providing a list of bin edges. In this example, we will create a histogram with unevenly spaced bins.

bins = [100, 150, 180, 195, 205, 220, 250, 300]
plt.hist(x, bins=bins, density=True, histtype='bar', rwidth=0.8)
plt.show()

Create two histograms with stacked bars

We can create two histograms with stacked bars by calling the hist function twice and setting the histtype parameter to 'barstacked'. In this example, we will create two histograms with stacked bars.

plt.hist(x, density=True, histtype='barstacked', rwidth=0.8)
plt.hist(w, density=True, histtype='barstacked', rwidth=0.8)
plt.show()

Summary

In this tutorial, we learned how to create a histogram using Matplotlib library. We also learned how to change the number of bins, the style of the histogram, and how to create a histogram with custom bin widths and stacked bars.