2.4. Examples: Lecture 2

2.4.1. Use of `matplotlib.pyplot`

• drawing_01.py

#!/usr/bin/python
'''
example on the use of matplotlib.pyplot
'''

import matplotlib.pyplot as plt

def main () :
    '''
    Funzione che implementa il programma principale
    '''
    fig, ax = plt.subplots (nrows = 1, ncols = 1)
    print (ax)
    plt.savefig ('drawing_01.png')
    plt.show ()
    

# ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 

    
if __name__ == "__main__":
    main ()

2.4.2. Drawing a function

• drawing_02.py

#!/usr/bin/python
'''
example on the use of matplotlib.pyplot
to draw a function
'''

import matplotlib.pyplot as plt
import numpy as np


def func (x) :
    return np.cos (x - np.pi / 2.)
    

# ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 

    
def main () :
    '''
    Funzione che implementa il programma principale
    '''
    fig, ax = plt.subplots (nrows = 1, ncols = 1)

    # preparing the set of points to be drawn 
    x_coord = np.linspace (0, 2 * np.pi, 10000)
    y_coord_1 = np.sin (x_coord)

    y_coord_2 = np.arange (0., x_coord.size)
    for i in range (x_coord.size):
        y_coord_2[i] = func (x_coord[i])

    # visualisation of the image
    ax.plot (x_coord, y_coord_1, label='sin (x)')
    ax.plot (x_coord, y_coord_2, linestyle = 'dashed', label='cos (x) - pi/2')
    ax.set_title ('Comparing trigonometric functions', size=14)
    ax.set_xlabel ('x')
    ax.set_ylabel ('y')
    ax.legend ()

    plt.savefig ('drawing_02.png')
    plt.show ()
    

# ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 

    
if __name__ == "__main__":
    main ()