感知機代碼實現

一、實現例子
李航《統計學方法》p29 例2.1
正例：x1=(3,3), x2=(4,3),
負例：x3=(1,1)
二、最終效果

三、代碼實現
import numpy as np
import matplotlib.pyplot as plt
p_x = np.array([[3, 3], [4, 3], [1, 1]])
y = np.array([1, 1, -1])
plt.figure()
for i in range(len(p_x)):
    if y[i] == 1:
        plt.plot(p_x[i][0], p_x[i][1], 'ro')
    else:
        plt.plot(p_x[i][0], p_x[i][1], 'bo')
 
w = np.array([1, 0])
b = 0
delta = 1
 
for i in range(100):
    choice = -1
    for j in range(len(p_x)):
        if y[j] != np.sign(np.dot(w, p_x[0]) + b):
            choice = j
            break
    if choice == -1:
        break
    w = w + delta * y[choice]*p_x[choice]
    b = b + delta * y[choice]
 
line_x = [0, 10]
line_y = [0, 0]
 
for i in range(len(line_x)):
    line_y[i] = (-w[0] * line_x[i]- b)/w[1]
 
plt.plot(line_x, line_y)
plt.savefig("picture.png")