Arrow annotations in Matplotlib

Introduction

Arrow annotations help point out important parts of a plot clearly. They make graphs easier to understand by showing exactly where to look.

You want to highlight a peak or special point in a line chart.

You need to explain a specific data point in a scatter plot.

You want to add notes or labels with arrows in a bar chart.

You want to guide viewers to a trend or anomaly in your graph.

Syntax

Matplotlib

plt.annotate(text, xy, xytext=null, arrowprops=null, **kwargs)

text is the label string you want to show.

xy is the point (x, y) to point the arrow at.

xytext is where the text label appears (optional).

arrowprops is a dictionary to style the arrow (optional).

Examples

Simple arrow pointing at (2, 8) with default text position.

Matplotlib

plt.annotate('Max value', xy=(2, 8))

Arrow from text at (4, 12) pointing to (3, 10) with a simple arrow style.

Matplotlib

plt.annotate('Peak', xy=(3, 10), xytext=(4, 12), arrowprops={'arrowstyle': '->'})

Arrow with red color and a small shrink effect for style.

Matplotlib

""plt.annotate('Important', xy=(1, 5), xytext=(0, 7),
             arrowprops={'facecolor': 'red', 'shrink': 0.05})"""

Sample Program

This code plots points and adds an arrow annotation pointing to the highest point at (2, 8). The arrow is blue and points from the text at (3, 9).

Matplotlib

import matplotlib.pyplot as plt

x = [0, 1, 2, 3, 4]
y = [1, 3, 8, 5, 2]

plt.plot(x, y, marker='o')

# Add arrow annotation pointing to the highest point
plt.annotate('Highest point', xy=(2, 8), xytext=(3, 9),
             arrowprops={'arrowstyle': '->', 'color': 'blue'})

plt.title('Example of Arrow Annotation')
plt.xlabel('X axis')
plt.ylabel('Y axis')
plt.grid(true)
plt.show()

Important Notes

You can customize arrow styles using arrowprops with keys like arrowstyle, color, and shrink.

If you don't set xytext, the text appears at the arrow point, which can overlap the marker.

Use plt.grid(true) to make the plot easier to read when adding annotations.

Summary

Arrow annotations help highlight points on plots clearly.

Use plt.annotate() with xy and optional xytext and arrowprops.

Customize arrows to make your graphs more informative and visually clear.