# -*- coding: utf-8 -*-
"""
Created on Thu Feb 05 17:44:21 2015

Exercice 15-1: Simulation d'une réaction en chaine

@author: grivet
"""

import numpy as np
import matplotlib.pyplot as plt

N = 1000; NR = 100
P1 = 0.1; P2 = 0.05
tab = np.zeros(N); n0 = np.zeros(NR); n1 = np.zeros(NR)
n2 = np.zeros(NR)
for ir in range(NR):
    for i in range(N):
        x = np.random.random()
        if x <= P1 and tab[i] == 0:
            tab[i] = 1
        x = np.random.random()
        if x <= P2 and tab[i] == 1:
            tab[i] = 2
    for i in range(N):
        if tab[i] == 0:
            n0[ir] += 1
        elif tab[i] == 1:
            n1[ir] += 1
        elif tab[i] == 2:
            n2[ir] += 1
        else:
            break
plt.plot(n0,'ok',n1,'ob',n2,'or')
#fig = plt.gca()
plt.title = 'Populations dans une réaction en chaine'
plt.xlabel("temps simulé")
plt.ylabel("populations")