Time for action – plotting a polynomial and its derivative

Let’s plot a polynomial and its first order derivative using the derive function with m as 1. We already did the first part in the previous Time for action tutorial. We want to have two different line styles to be able to discern what is what.

  1. Create and differentiate the polynomial.
    func = np.poly1d(np.array([1, 2, 3, 4]).astype(float))
func1 = func.deriv(m=1)
x = np.linspace(-10, 10, 30)
y = func(x)
y1 = func1(x)
  2. Plot the polynomial and its derivative in two different styles: red circles and green dashes. You cannot see the colors in a print copy of this book so you will have to try it out for yourself.
    plt.plot(x, y, 'ro’, x, y1, 'g--’)
plt.xlabel('x’)
plt.ylabel('y’)
plt.show()

    The graph again with polynomial coefficients 1, 2, 3, and 4:

    Time for action – plotting a polynomial and its derivative

What just happened?

We plotted a polynomial and its derivative using two different line styles and one call of the plot function (see polyplot2.py):

import numpy as np
import matplotlib.pyplot as plt

func = np.poly1d(np.array([1, 2, 3, 4]).astype(float))
func1 = func.deriv(m=1)
x = np.linspace(-10, 10, 30)
y = func(x)
y1 = func1(x)

plt.plot(x, y, 'ro’, x, y1, 'g--’)
plt.xlabel('x’)
plt.ylabel('y’)
plt.show()
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