Adding arrows

Adding text boxes can help you to annotate a figure. However, to show a specific part of a picture, nothing beats the use of an arrow. In this recipe, we will show you how to add arrows on a figure.

How to do it...

matplotlib has a function to draw arrows with the pyplot.annotate() function as shown in the following code snippet:

import numpy as np
import matplotlib.pyplot as plt

X = np.linspace(-4, 4, 1024)
Y = .25 * (X + 4.) * (X + 1.) * (X - 2.)

plt.annotate('Brackmard minimum',
ha = 'center', va = 'bottom',
xytext = (-1.5, 3.),
xy = (0.75, -2.7),
arrowprops = { 'facecolor' : 'black', 'shrink' : 0.05 })

plt.plot(X, Y)
plt.show()

This script annotates a curve with text and an arrow, as shown in the following graph:

How it works...

The pyplot.annotate() function shows text working on the same lines as pyplot.text(). However, an arrow is also rendered. The text to be displayed is the first parameter. The xy parameter specifies the arrow's destination. The xytext parameter specifies...