Path simplification in Matplotlib

Introduction

Path simplification helps to reduce the number of points in a line or shape. This makes plots faster and easier to understand.

When you have a very detailed line plot with many points and want to make it simpler.

When you want to speed up drawing complex shapes in a plot.

When you want to reduce file size of saved plots by simplifying paths.

When you want to improve plot readability by removing unnecessary points.

Syntax

Matplotlib

Line2D.set_path_simplify(True)
# or
Path.set_simplify(True)

Path simplification is often enabled by default in matplotlib for line plots.

You can control the simplification tolerance with set_path_simplify_threshold().

Examples

This example plots a smooth sine wave with many points. Path simplification reduces points automatically.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 10, 1000)
y = np.sin(x)

plt.plot(x, y)  # Path simplification is on by default
plt.show()

You can explicitly turn on path simplification for a line.

Matplotlib

line, = plt.plot(x, y)
line.set_path_simplify(True)  # explicitly enable simplification
plt.show()

This sets how much the path can deviate when simplifying. Smaller means more points kept.

Matplotlib

line.set_path_simplify_threshold(0.1)  # set tolerance for simplification

Sample Program

This code plots the same noisy sine wave twice: once without path simplification and once with it. You can see the simplified line is smoother and faster to draw.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

# Create many points for a noisy line
x = np.linspace(0, 10, 1000)
y = np.sin(x) + np.random.normal(0, 0.1, x.size)

# Plot without simplification
line1, = plt.plot(x, y, label='No simplification')
line1.set_path_simplify(False)

# Plot with simplification
line2, = plt.plot(x, y + 1.5, label='With simplification')
line2.set_path_simplify(True)
line2.set_path_simplify_threshold(0.1)

plt.legend()
plt.title('Path Simplification Example')
plt.show()

Important Notes

Path simplification works by removing points that do not change the shape much.

Too much simplification can lose important details, so adjust the threshold carefully.

Path simplification mainly affects line plots, not scatter plots.

Summary

Path simplification reduces points in lines to speed up plotting.

It is enabled by default but can be controlled with methods on Line2D objects.

Adjust the simplification threshold to balance detail and performance.