import matplotlib.pyplot as plt
import numpy as np

dist_A = np.zeros(20)
dist_S = np.zeros(20)
dist_S[0] = 100 #Turtle start 100 meters ahead
number = 100 

# Fill array with numbers [0, 100, 10, 1 ,0.1, 0.01, ...]
for i in range(1, 20): 

    dist_A[i] = dist_A[i-1] + number
    number = number/10 #  Reduce number with factor of 10
    dist_S[i] = dist_S[i-1] + number

plt.close('all')
plt.figure(1, figsize=(12, 9))
plt.plot(dist_S - dist_A, 'o-', label=('dist_S - dist_A'))
plt.legend()
plt.xlabel('Index in array')
plt.ylabel('[m]')
plt.grid()
# plt.savefig('plot_akilles.pdf')
plt.show()