exponential.py

"""
    Code by Tae-Hwan Hung(@graykode)
    https://en.wikipedia.org/wiki/Exponential_distribution
"""
import numpy as np
from matplotlib import pyplot as plt

def exponential(x, lamb):
    y = lamb * np.exp(-lamb * x)
    return x, y, np.mean(y), np.std(y)

for lamb in [0.5, 1, 1.5]:

    x = np.arange(0, 20, 0.01, dtype=np.float)
    x, y, u, s = exponential(x, lamb=lamb)
    plt.plot(x, y, label=r'$\mu=%.2f,\ \sigma=%.2f,'
                         r'\ \lambda=%d$' % (u, s, lamb))
plt.legend()
plt.savefig('graph/exponential.png')
plt.show()