李航感知机对偶形式python代码

#author：xinxinzhang

import numpy as np
def loadData():  #加载数据
    X=np.mat([[3,3],
              [4,3],
              [1,1]])
    Y=[1,1,-1]
    return X,Y
def Gram(X):  #计算Gram矩阵
    m,n=np.shape(X)
    G=[None]*m
    for i in range(m):
        G[i]=[0]*m
        for j in range(m):
            G[i][j]=int(np.dot(X[i],X[j].T))  #G=[xi*xj]
    return np.mat(G)
def perceptron_pair(G,X,Y):   #感知机对偶算法
    m, n = np.shape(X)
    alpha=np.zeros(m)        #初始化alpha，b
    b=0
    isfind=False
    while not isfind:

        for i in range(m):
            s=0
            for j in range(m):
                s+=alpha[j]*Y[j]*G[j,i]
            s+=b
            
            if Y[i]*s<=0:    #误分条件
                alpha[i]+=1   #更新alpha，b
                b+=Y[i]
                print(alpha,b)
                break
            elif i == m - 1:  #直到没有误分数据
                print(alpha,b)  #打印alpha，b
                isfind=True
            


X,Y=loadData()
G=Gram(X)
# print('G',G)
perceptron_pair(G,X,Y)

运行结果如图所示：