3D axes with projection='3d' in Matplotlib

Introduction

We use 3D axes to show data in three dimensions. This helps us see relationships that are hard to understand in flat 2D charts.

When you want to visualize points or shapes in space, like stars or buildings.

When you have three variables and want to see how they relate together.

When you want to show a surface or a 3D curve.

When you want to explore data from different angles by rotating the view.

Syntax

Matplotlib

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

The key part is projection='3d' which tells matplotlib to create 3D axes.

You need to import Axes3D from mpl_toolkits.mplot3d to enable 3D plotting.

Examples

Create a figure and add one 3D subplot.

Matplotlib

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

Create a bigger figure with 3D axes.

Matplotlib

fig = plt.figure(figsize=(8,6))
ax = fig.add_subplot(111, projection='3d')

Create two 3D plots side by side.

Matplotlib

fig = plt.figure()
ax1 = fig.add_subplot(121, projection='3d')
ax2 = fig.add_subplot(122, projection='3d')

Sample Program

This program creates a 3D surface plot of a wave pattern. It shows how to set up 3D axes and plot a surface using plot_surface.

Matplotlib

from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
import numpy as np

# Create data
x = np.linspace(-5, 5, 50)
y = np.linspace(-5, 5, 50)
X, Y = np.meshgrid(x, y)
Z = np.sin(np.sqrt(X**2 + Y**2))

# Create figure and 3D axes
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

# Plot surface
surf = ax.plot_surface(X, Y, Z, cmap='viridis')

# Add labels
ax.set_xlabel('X axis')
ax.set_ylabel('Y axis')
ax.set_zlabel('Z axis')

# Show plot
plt.show()

Important Notes

3D plots can be rotated interactively in the plot window to see different angles.

Not all matplotlib plot types support 3D, so use functions like plot_surface, scatter, or plot on 3D axes.

Summary

Use projection='3d' to create 3D axes in matplotlib.

3D plots help visualize data with three variables or spatial shapes.

You can plot surfaces, scatter points, and lines in 3D.