確率分布書き方

ポアソン分布の作り方

import scipy.stats
import numpy as np
import matplotlib.pyplot as plt
#figsize(12.5,4)

lambda_ = [1.5, 4.25]
colors = ["#348ABD","#A60628"]

a = np.arange(16)
plt.bar(a,scipy.stats.poisson.pmf(a,lambda_[0]),color=colors[0],label="$\lambda=%.1f$"%lambda_[0],alpha=0.60,edgecolor=colors[0],lw="3")
plt.bar(a,scipy.stats.poisson.pmf(a,lambda_[1]),color=colors[1],label="$\lambda=%.1f$"%lambda_[1],alpha=0.60,edgecolor=colors[1],lw="3")

plt.xticks(a+0.4,a)
plt.legend()
plt.ylabel("Probability of $k$")#kの確率
plt.xlabel("$k$")
plt.title("Probability mass function of a Poisson random variable, differing $\lambda$ values")
plt.show()

指数分布

import numpy as np
import matplotlib.pyplot as plt
import scipy.stats

a = np.linspace(0,4,100)
lambda_ = [0.5,1]
colors=["#348ABD","#A60628"]

for l,c in zip(lambda_,colors):
    plt.plot(a,scipy.stats.expon.pdf(a,scale=1./l),lw=3,color=c,label="$\lambda=%.1f$"%l)
    plt.fill_between(a,scipy.stats.expon.pdf(a,scale=1./l),color=c,alpha=.33)

plt.legend()
plt.ylabel("Probability density function at $z$")#zにおける確率密度関数
plt.xlabel("$z$")
plt.ylim(0,1.2)
plt.title("Probability density function of an exponential random variable, differing $\lambda$ values")
plt.savefig("exponential_distribution.png")