# Plotting Mathematical Functions With Matplotlib

The following source code shows how to plot two mathematical functions (one linear and one quadratic) using the Matplotlib library, save the result to a PNG image, and display it on the screen. The functions are:

• Quadratic: $f_1(x) = 2x^2 + 5x - 2$

• Linear: $f_2(x) = 4x + 1$

This is the resulting image:

And the code:

 import matplotlib.pyplot as plt    # Quadratic function.  def f1(x):      return 2*(x**2) + 5*x - 2    # Linear function.  def f2(x):      return 4*x + 1    # The X values to be plotted.  x = range(-10, 15)    # Plot both functions.  # The second argument calculates the Y value for each of  # the X values defined above.  plt.plot(x, [f1(i) for i in x])  plt.plot(x, [f2(i) for i in x])    # Configure the color of the axes.  plt.axhline(0, color="black")  plt.axvline(0, color="black")    # The range of values shown by each axis.  plt.xlim(-10, 10)  plt.ylim(-10, 10)    # Save the plot as a PNG image.  plt.savefig("output.png")    # Show the result.  plt.show() 

The Matplotlib library required by this code can be installed via python -m pip install matplotlib.