HORIZONTAL LINES IN Matplotlib

Listing 5.5 displays the contents of hlines1.py that illustrates how to plot horizontal lines using Matplotlib. Recall that the equation of a non-vertical line in the 2D plane is y = m*x + b, where m is the slope of the line and b is the y-intercept of the line.

LISTING 5.5: hlines1.py

import numpy as np
import matplotlib.pyplot as plt

# top line
x1 = np.linspace(-5,5,num=200)
y1 = 4 + 0*x1

# middle line
x2 = np.linspace(-5,5,num=200)
y2 = 0 + 0*x2

# bottom line
x3 = np.linspace(-5,5,num=200)
y3 = -3 + 0*x3

plt.axis([-5, 5, -5, 5])
plt.plot(x1,y1)
plt.plot(x2,y2)
plt.plot(x3,y3)
plt.show()

Listing 5.5 uses the np.linspace() API in order to generate a list of 200 equally spaced numbers for the horizontal axis, all of which are between -5 and 5. The three lines defined via the variables y1, y2, and y3, are defined in terms of the variables x1, x2, and x3, respectively.

Figure 5.2 displays three horizontal line segments whose equations are contained in...