How to annotate a range of the X-axis in Matplotlib?

Annotating a range of the X-axis in Matplotlib helps highlight specific sections of your data. This is useful for marking important intervals, peaks, or regions of interest in your plots.

Basic Range Annotation

Use annotate() with arrow properties to create a visual range indicator ?

import matplotlib.pyplot as plt
import numpy as np

plt.rcParams["figure.figsize"] = [7.50, 3.50]
plt.rcParams["figure.autolayout"] = True

# Create data points
xx = np.linspace(0, 10)
yy = np.sin(xx)

fig, ax = plt.subplots(1, 1)

ax.plot(xx, yy)
ax.set_ylim([-2, 2])

# Annotate range with arrow
ax.annotate('', xy=(5, 1.5), xytext=(8, 1.5),
            xycoords='data', textcoords='data',
            arrowprops={'arrowstyle': '<|-|>', 'color': 'red'})

# Add range label
ax.annotate('Range of Interest', xy=(6.5, 1.7), ha='center', va='center', color='red')

plt.show()

Multiple Range Annotations

You can annotate multiple ranges with different colors and labels ?

import matplotlib.pyplot as plt
import numpy as np

# Create sample data
x = np.linspace(0, 10, 100)
y = np.sin(x) * np.exp(-x/10)

fig, ax = plt.subplots(1, 1, figsize=(8, 4))

ax.plot(x, y, 'b-', linewidth=2)

# First range annotation
ax.annotate('', xy=(1, 0.6), xytext=(3, 0.6),
            arrowprops={'arrowstyle': '<|-|>', 'color': 'red', 'lw': 2})
ax.annotate('Peak Region', xy=(2, 0.7), ha='center', color='red', fontsize=10)

# Second range annotation
ax.annotate('', xy=(6, -0.4), xytext=(9, -0.4),
            arrowprops={'arrowstyle': '<|-|>', 'color': 'green', 'lw': 2})
ax.annotate('Decay Region', xy=(7.5, -0.5), ha='center', color='green', fontsize=10)

ax.set_xlabel('X-axis')
ax.set_ylabel('Y-axis')
ax.grid(True, alpha=0.3)

plt.show()

Key Parameters

Conclusion

Use annotate() with arrowstyle='<|-|>' to create range indicators on your X-axis. This technique is perfect for highlighting specific data intervals or marking regions of interest in your matplotlib plots.