otamn - 経済統計練習帳

import matplotlib.pyplot as plt
import numpy as np
import math
 
def comb(n, r):
   return math.factorial(n) / (math.factorial(n - r) * math.factorial(r))
 
def binomial(p):
   def f(n, x):
       prob = comb(n, x) * p ** x * (1 - p) ** (n - x)
       return prob
   return f
 
p = 0.5
L = []
trial_count = (10, 20, 30, 40, 50)
colors = ["r", "g", "b", "c", "y"]
f = binomial(p)
 
for n in trial_count :
   L.append([f(n, x) for x in range(n)])
 
for prob, color in zip(L, colors) :
   plt.plot(prob, color)
 
ax = plt.axes()
ax.set_xlim(0, 50)
ax.set_ylim(-0.05, 0.3)
 
plt.title(r'$\mathrm{Binomial Distribution}\ P=%f$' % (p))
plt.xlabel('Trial')
plt.ylabel('Probability')
plt.legend([str(n) for n in trial_count])
plt.show()