二类分类中基尼指数、 熵之半和分类误差率的关系

import numpy as np
from matplotlib import pyplot as plt 
import matplotlib as mpl
mpl.rcParams['font.sans-serif'] = ['simHei']
mpl.rcParams['axes.unicode_minus'] = False

p = np.linspace(0.0001, 0.9999 ,50)
Gini = 2 * p * (1-p)
H = (-p * np.log2(p) - (1 - p) * np.log2(1 - p))/2.0
x1 = np.linspace(0,0.5,50)
y1 = x1
x2 = np.linspace(0.5,1,50)
y2 = 1- x2

plt.figure(figsize=(10,5))
plt.plot(p, Gini, 'r-', label='基尼指数')
plt.plot(p, H, 'b-', label='半熵')
plt.plot(x1, y1, 'g-', label='分类误差率')
plt.plot(x2, y2, 'g-')
plt.legend()
plt.xlim(-0.01, 1.01)
plt.ylim(0, 0.51)
plt.show()