Annotation with arrows in Matplotlib

Introduction

We use annotations with arrows to point out important parts of a chart. It helps make the chart easier to understand.

You want to highlight a peak or valley in a line chart.

You need to explain a special point on a scatter plot.

You want to add notes to a bar chart to show extra info.

You want to guide the viewer’s attention to a specific data point.

You want to label parts of a plot clearly with arrows.

Syntax

Matplotlib

plt.annotate(text, xy, xytext=None, arrowprops=None, **kwargs)

text is the label string you want to show.

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

Examples

This adds an annotation 'Peak' pointing to (2, 8) with the text shown at (3, 10).

Matplotlib

plt.annotate('Peak', xy=(2, 8), xytext=(3, 10), arrowprops=dict(facecolor='black'))

Annotation with default text position and a simple arrow style.

Matplotlib

plt.annotate('Important', xy=(1, 5), arrowprops=dict(arrowstyle='->'))

Arrow with red color and a small shrink effect near the point.

Matplotlib

plt.annotate('Note', xy=(4, 7), xytext=(5, 9), arrowprops=dict(color='red', shrink=0.05))

Sample Program

This code plots a line with points and adds an annotation with an arrow pointing to the highest point on the line.

Matplotlib

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [2, 8, 5, 10, 7]

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

# Annotate the highest point
max_y = max(y)
max_x = x[y.index(max_y)]
plt.annotate('Highest point', xy=(max_x, max_y), xytext=(max_x+0.5, max_y+1),
             arrowprops=dict(facecolor='blue', shrink=0.05))

plt.title('Line plot with annotation')
plt.xlabel('X axis')
plt.ylabel('Y axis')
plt.grid(True)
plt.show()

Important Notes

You can customize arrow styles using arrowprops dictionary.

If xytext is not given, the text appears at the point xy.

Use shrink in arrowprops to adjust arrow length near the point.

Summary

Annotations with arrows help explain charts clearly.

Use plt.annotate() with xy and arrowprops to add arrows.

You can place text separately from the arrow tip using xytext.