matlab 实现感知机线性二分类算法（Perceptron）

function W = Perceptron(X,y,learnRate,maxStep)

% Perceptron.m
% Perception Learning Algorithm(感知机)
% X一行为一个样本，y的取值{-1,+1} 
% learnRate：学习率
% maxStep:最大迭代次数
  
[n,m] = size(X);  
X = [X ones(n,1)];  
W=zeros(m+1,1);  

for step = 1:maxStep
    flag = true;
    for index = 1:n  
        if sign(X(index,:) * W) ~= y(index)  
            flag = false;  
            W = W + learnRate * y(index) .* X(index,:)‘;
        end  
    end  
    if flag == true  
        break;  
    end  
end  

%%% test
close;
clear;
clc;

X = [0,0;1,0;2,0;1,1;0,2;1,3;2,4;4,2];
y = [-1,-1,-1,-1,-1,1,1,1];

n = size(y,2);
for i = 1:n
    if y(i) == 1
        plot(X(i,1),X(i,2),‘rs‘);
    end
    if y(i) == -1
        plot(X(i,1),X(i,2),‘b*‘);
    end
    hold on;
end

W = Perceptron(X,y,1,500);

xline = linspace(0,5,50);
yline = -W(1)/W(2) * xline - W(3)/W(2); % w1*x1+w2*x2+w3=0,x2看成yline

plot(xline,yline);