File:Poisson pmf.svg

import numpy as np
import matplotlib.pyplot as plt
import scipy.special as sp
 
X = np.arange(0,21)
 
col = {1: 'orange', 4: 'purple', 10: 'lightblue'}
 
 
##                                                                                
## PMF                                                                            
##                                                                                
 
plt.clf()
plt.figure(figsize=(4,3.2))
plt.axes([0.17,0.13,0.79,0.8])
plt.hold(True)
 
A = []
for L in 1,4,10:
 
    P = -L + X*np.log(L) - sp.gammaln(X+1)
    P = np.exp(P)
 
    plt.plot(X, P, '-', color='grey')
    a = plt.plot(X, P, 'o', color=col[L])
    A.append(a)
 
plt.xlabel("k")
plt.ylabel(r"P(X=k)")
 
bx = plt.legend(A, (r"$\lambda=1$", r"$\lambda=4$", r"$\lambda=10$"),\
                numpoints=1, handletextpad=0, loc="upper right")
bx.draw_frame(False)
plt.xlim(-1,21)
 
plt.savefig("poisson_pmf.pdf")
plt.savefig("poisson_pmf.svg")