逻辑回归的实现

逻辑回归：0-1分类

通过学习求出参数theta，从而求出sigmoid函数

1.求theta[j]*x[i][j]

2.根据sigmoid函数求出h

3.求出theta[j]=theta[j]+0.01*(y[i]-h)*x[i][j]

4.求出假设函数（拟合直线）

代码如下:

#include"math.h"

#include "stdio.h"

#define M 110

#define N 3

double sigmoidFunction(double x)

{

      double h;

      h=1/(1+exp(-x));

      return h;

}

int main()

{

      double x[M][N];

      int i,j,k;

      double theta[3]={0.0,0.0,0.0};

      double h=0.0;

      FILE *fp;

      fp=fopen("ex2data1.txt","r");

      if(fp==NULL)//打开文件成功返回文件指针fp，失败返回NULL

      {

            return -1;

      }

      for(i=0;i

     {

            fscanf(fp,"%lf,%lf,%lf",&x[i][0],&x[i][1],&x[i][2]);

            fscanf(fp,"\n");

     }

     fclose(fp);

     printf("%lf",x[1][2]);

     for(k=0;k<1000;k++)

     {

           for(i=0;i

           {

                for(j=0;j<3;j++)

                {

                      h=theta[j]*x[i][j];

                }

                h= sigmoidFunction(h);

                for(j=0;j<3;j++)

                {

                       theta[j]+=0.01*(x[i][j]-h)*x[i][j];

                }

           }

      }

}