基于matlab的逻辑回归示例

最近研究机器学习算法，属于小白，学习了“寒小阳”博主的文章（地址：http://blog.youkuaiyun.com/han_xiaoyang/article/details/49123419）后，对机器学习的逻辑回归有了个大概的认识，再借助另一位博主“ Earendil ”（地址：https://www.cnblogs.com/earendil/p/8268757.html）对于其中公式的详细推导，试着用matlab语言自己实现一遍，现与大家分享，代码如下：
clc
clear all
close all
data1 = importdata(‘data1.txt’);
%归一化
data1(:,1) = (data1(:,1)- mean(data1(:,1)))./ std(data1(:,1));
data1(:,2) = (data1(:,2)- mean(data1(:,2)))./ std(data1(:,2));
[m,n] = size(data1);
figure
for row = 1:m
if data1(row,3) == 1
plot(data1(row,1),data1(row,2),’.’);
hold on
else
plot(data1(row,1),data1(row, 2),‘x’);
hold on
end
end
%矩阵化
x0 = ones(m,1);
X = [x0,data1(:,1),data1(:,2)];
[m1,n1] = size(X);
theta = ones(n1,1);%初始化
alpha = 0.001;%步长
for