Histograms

Matplotlib Basics

1 min read

Published Oct 5 2025, updated Aug 17 2026

ChartsGraphsMatplotlibNumPyPandasPythonVisualisation

A histogram visualises the distribution of numerical data — it shows how many data points fall into a range of values (called bins).

Instead of plotting individual points, it groups values and displays the frequency in vertical bars.

Syntax:

plt.hist(x, bins=None, range=None, density=False, color=None, edgecolor=None, alpha=None, histtype='bar')

Parameters:

x = Data to plot
bins = Number of bins (int) or explicit bin edges
range = Lower and upper range of bins
density = Normalise histogram (area = 1)
color = Fill colour
edgecolor = Outline color
alpha = Transparency
histtype = Type of histogram: 'bar', 'step', 'stepfilled'
label = Legend label

Basic histogram example

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data)plt.title("Basic Histogram")plt.xlabel("Value")plt.ylabel("Frequency")plt.show()

This automatically chooses 10 bins by default.

matplotlib histogram chart basic example

Custom number of bins

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=20, color='skyblue', edgecolor='black')plt.title("Histogram with 20 Bins")plt.show()

matplotlib histogram chart custom bins example

Define custom bin edges

You can define the exact cut points:

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)bins = [-3, -2, -1, 0, 1, 2, 3]plt.hist(data, bins=bins, color='salmon', edgecolor='black')plt.title("Custom Bin Edges")plt.show()

matplotlib histogram chart custom bin edges example

Change Colour and Edge

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=15, color='orange', edgecolor='blue')plt.title("Styled Histogram")plt.show()

matplotlib histogram chart styled example

Multiple histograms on the same plot

You can overlay histograms to compare distributions:

import matplotlib.pyplot as pltimport numpy as npdata1 = np.random.normal(0, 1, 1000)data2 = np.random.normal(2, 1, 1000)plt.hist(data1, bins=20, alpha=0.5, label='Group A')plt.hist(data2, bins=20, alpha=0.5, label='Group B')plt.legend()plt.title("Multiple Histograms (Overlayed)")plt.show()

Use alpha for transparency so both remain visible.

matplotlib histogram chart multiple example

Stacked Histograms

Stack multiple datasets to see combined distribution:

import matplotlib.pyplot as pltimport numpy as npdata1 = np.random.normal(0, 1, 1000)data2 = np.random.normal(2, 1, 1000)plt.hist([data1, data2], bins=20, stacked=True, color=['skyblue', 'lightcoral'], label=['Group A', 'Group B'])plt.legend()plt.title("Stacked Histogram")plt.show()

matplotlib histogram chart stacked example

Step and step-filled styles

Step:

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=30, histtype='step', color='navy', linewidth=2)plt.title("Step Histogram")plt.show()

Step Filled:

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=30, histtype='stepfilled', color='lightgreen', alpha=0.7)plt.title("Step-Filled Histogram")plt.show()

Normalised histogram (density plot)

If you want the area under the curve = 1, use density=True. This is common for probability distributions.

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=30, density=True, color='plum', edgecolor='black')plt.title("Normalised Histogram (Density=True)")plt.ylabel("Probability Density")plt.show()

matplotlib histogram chart density example

Cumulative Histogram

To show cumulative frequencies.

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=30, cumulative=True, color='lightblue', edgecolor='black')plt.title("Cumulative Histogram")plt.show()

matplotlib histogram chart cumulative example

Horizontal histogram

import matplotlib.pyplot as pltimport numpy as npdata = np.random.randn(1000)plt.hist(data, bins=20, orientation='horizontal', color='lime', edgecolor='black')plt.title("Horizontal Histogram")plt.show()

matplotlib histogram chart horizontal example