Time for action – drawing Lissajous curves

The Lissajous figures are determined by four parameters A, B, a, and b. Let's set A and B to 1 for simplicity:

  1. Initialize t with the linspace function from -pi to pi with 201 points:
    a = float(sys.argv[1])
b = float(sys.argv[2])
t = np.linspace(-np.pi, np.pi, 201)
  2. Calculate x with the sin function and np.pi:
    x = np.sin(a * t + np.pi/2)
  3. Calculate y with the sin function:
    y = np.sin(b * t)
  4. Matplotlib will be covered later in Chapter 9, Plotting with Matplotlib. Plot as shown here:
    Time for action – drawing Lissajous curves
    plot(x, y)
show()

    The result for a = 9 and b = 8:

What just happened?

We plotted the Lissajous curve with the previously mentioned parametric equations where A=B=1, a=9, and, b=8. We used the sin and linspace functions as well as the NumPy pi constant (see lissajous.py):

import numpy as np
from matplotlib.pyplot import plot
from matplotlib.pyplot import show
import sys

a = float(sys.argv[1])
b = float(sys.argv[2])
t = np.linspace(-np.pi, np.pi, 201)
x = np.sin(a * t + np.pi/2)
y = np.sin(b * t)
plot(x, y)
show()
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