matplotlib.pyplot.arrow() in Python

Matplotlib is a very powerful plotting library Python, widely used for data visualization and statistical analysis. One of its useful functions is arrow(), which lets you add arrows to your plots to highlight or point out specific data points or trends.

This article explains how to use the arrow() function, its syntax and how to customize arrows using various parameters.

Example 1: Basic Arrow Addition

This example shows how to add a simple arrow to a plot.

import matplotlib.pyplot as plt

# Data points
x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]

# Plot the data
plt.plot(x, y)

# Add an arrow starting at (2, 4) with dx = 2 and dy = 2, and a specified width
plt.arrow(2, 4, 2, 2, width=0.05)

# Display the plot
plt.show()

Output: 

Explanation:

• The arrow starts at coordinates (2, 4).
• The arrow extends 2 units in both the x and y directions.
• The width of the arrow shaft is set to 0.05.

Syntax

matplotlib.pyplot.arrow(x, y, dx, dy, **kwargs) 

Parameters: 

• x, y: The x and y coordinates of the arrow base. 
• dx, dy: The length of the arrow along x and y direction. 
• **kwargs: Optional arguments that helps in adding properties to arrow, like adding color to arrow, changing width of arrow.

Examples of arrow() function

Example 1 : Adjusting Arrow Head Width

This example demonstrates how to increase the arrowhead width for better visibility.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]
plt.plot(x, y)

# Add an arrow with a larger head width (0.2) and a shaft width of 0.05
plt.arrow(2, 4, 2, 2, head_width=0.2, width=0.05)

plt.show()

Output: 

Explanation:

• The arrowhead width is increased toB.
• The arrow's base, displacement, and shaft width remain the same as in Example 1.

Example 2: Changing Arrow Edge Color

This example shows how to change the arrow's edge color to green.

import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [2, 4, 6, 8, 10]
plt.plot(x, y)

# Add an arrow with a green edge color
plt.arrow(2, 4, 2, 2, head_width=0.2, width=0.05, ec='green')

plt.show()

Output: 

Explanation:

• The arrow's edge color (ec) is set to green.
• Other properties such as head width and shaft width are maintained.