《机器学习实战》读书笔记—k近邻算法c语言实现（win下）

#include <stdio.h>#include <io.h> #include <math.h>#include <stdlib.h>#define K 10//kNN中选取最近邻居的个数#define LINE 1024//每个文件字符数const char *to_search_train = "F:\\kNN\\train\\*.txt";        //train数据地址const char *to_search_test = "F:\\kNN\\test\\*.txt";          //test数据地址 struct//定义结构体 储存train数据和标签{int train_mat[2000][LINE];//矩阵每一行都是1*LINE的矩阵int train_label[2000];//储存每个数据的标签}Train;struct//定义结构体 储存test数据和标签{int test_mat[2000][LINE];int test_label[2000];}Test;float mat_dist[1000][2000];//定义距离矩阵，储存每个test数据到每个train数据的距离//定义子函数，功能：将每个test数据与所有train数据的距离进行排序，选取距离最小的前K个，这K个数据标签类型最多的，将此标签返回给主函数int BubbleSort(float mat_dist_row[], int label[],int num_train) {  int i,j,k;int temp,temp_label;int num[K] = {0};int max = 0;int label_final = 0;        for(i = 0;i < num_train;i++)   //冒泡排序，距离从小到大，同时将label对应跟随    {          for(j = i+1;j < num_train;j++)          {              if(mat_dist_row[i] > mat_dist_row[j])               {                  temp = mat_dist_row[i];                  mat_dist_row[i] = mat_dist_row[j];                  mat_dist_row[j] = temp;temp_label = label[i];                  label[i] = label[j];                  label[j] = temp_label;            }          }      }for (k = 0;k < K;k++)//统计前K个数据，各种标签的个数{switch(label[k]){case 0:num[0]++;break;case 1:num[1]++;break;case 2:num[2]++;break;case 3:num[3]++;break;case 4:num[4]++;break;case 5:num[5]++;break;case 6:num[6]++;break;case 7:num[7]++;break;case 8:num[8]++;break;case 9:num[9]++;break;default:break;}}max = num[0];for(i = 0;i < K;i++)//标签类型最多的，选择次标签      {if (num[i] > max ){max = num[i];label_final = i;}}return label_final;}int main()        {     FILE *fp;    int c;//用于逐个读入字符数据int train_i = 0,train_j = 0,test_i = 0,test_j = 0;//用于循环int count_train = 0,count_test = 0;//用于统计train和test文件的个数int i,j,k,l;//用于循环int sum = 0;//距离求和int update_label[2000];//每次调用函数，更新labelint classifier;//记录返回的标签类型int count = 0;//错误的个数float rate;//错误率char str_adr[255];                                          //fopen函数读入文件名时地址long handle;                                                //用于查找的句柄       struct _finddata_t fileinfo;//文件信息的结构体      handle = _findfirst(to_search_train,&fileinfo);//第一次查找sprintf(str_adr, "F:\\kNN\\train\\%s", fileinfo.name);//文件名赋给str_adrif(-1 == handle){printf("File not exit\n");}else{switch(fileinfo.name[0])//给第一个文件赋予标签{case '0':Train.train_label[count_train] = 0;break;case '1':Train.train_label[count_train] = 1;break;case '2':Train.train_label[count_train] = 2;break;case '3':Train.train_label[count_train] = 3;break;case '4':Train.train_label[count_train] = 4;break;case '5':Train.train_label[count_train] = 5;break;case '6':Train.train_label[count_train] = 6;break;case '7':Train.train_label[count_train] = 7;break;case '8':Train.train_label[count_train] = 8;break;case '9':Train.train_label[count_train] = 9;break;default:break;}count_train++;if((fp = fopen(str_adr,"r")) == NULL)printf("Error!Can't open the file!\n");else//将文件中'0'和'1'字符转化为数字0，1，并储存{while((c = fgetc(fp)) != EOF){if(c == '0' || c == '1'){Train.train_mat[train_i][train_j] = c - '0';train_j++;}}}fclose(fp);while(!_findnext(handle,&fileinfo))               //循环查找其他符合的文件，知道找不到其他的为止  {train_j = 0;train_i++;sprintf(str_adr, "F:\\kNN\\train\\%s", fileinfo.name);switch(fileinfo.name[0])//给后面文件赋予标签{case '0':Train.train_label[count_train] = 0;break;case '1':Train.train_label[count_train] = 1;break;case '2':Train.train_label[count_train] = 2;break;case '3':Train.train_label[count_train] = 3;break;case '4':Train.train_label[count_train] = 4;break;case '5':Train.train_label[count_train] = 5;break;case '6':Train.train_label[count_train] = 6;break;case '7':Train.train_label[count_train] = 7;break;case '8':Train.train_label[count_train] = 8;break;case '9':Train.train_label[count_train] = 9;break;default:break;}if((fp = fopen(str_adr,"r")) == NULL)printf("Error!Can't open the file!\n");else//将文件中'0'和'1'字符转化为数字0，1，并储存{while((c = fgetc(fp)) != EOF){if(c == '0' || c == '1'){Train.train_mat[train_i][train_j] = c - '0';train_j++;}}}count_train++;fclose(fp);}  }_findclose(handle);                                       //下面重复上面文件读入和储存的过程，读入并储存所有test数据handle = _findfirst(to_search_test,&fileinfo);         sprintf(str_adr, "F:\\kNN\\test\\%s", fileinfo.name);if(-1 == handle){printf("File not exit\n");}else{switch(fileinfo.name[0]){case '0':{Test.test_label[count_test] = 0;break;}case '1':{Test.test_label[count_test] = 1;break;}case '2':{Test.test_label[count_test] = 2;break;}case '3':{Test.test_label[count_test] = 3;break;}case '4':{Test.test_label[count_test] = 4;break;}case '5':{Test.test_label[count_test] = 5;break;}case '6':{Test.test_label[count_test] = 6;break;}case '7':{Test.test_label[count_test] = 7;break;}case '8':{Test.test_label[count_test] = 8;break;}case '9':{Test.test_label[count_test] = 9;break;}default:break;}count_test++;if((fp = fopen(str_adr,"r")) == NULL)printf("Error!Can't open the file!\n");else{while((c = fgetc(fp)) != EOF){if(c == '0' || c == '1'){Test.test_mat[test_i][test_j] = c - '0';test_j++;}}}fclose(fp);while(!_findnext(handle,&fileinfo))                {test_j = 0;test_i++;sprintf(str_adr, "F:\\kNN\\test\\%s", fileinfo.name);switch(fileinfo.name[0]){case '0':{Test.test_label[count_test] = 0;break;}case '1':{Test.test_label[count_test] = 1;break;}case '2':{Test.test_label[count_test] = 2;break;}case '3':{Test.test_label[count_test] = 3;break;}case '4':{Test.test_label[count_test] = 4;break;}case '5':{Test.test_label[count_test] = 5;break;}case '6':{Test.test_label[count_test] = 6;break;}case '7':{Test.test_label[count_test] = 7;break;}case '8':{Test.test_label[count_test] = 8;break;}case '9':{Test.test_label[count_test] = 9;break;}default:break;}if((fp = fopen(str_adr,"r")) == NULL)printf("Error!Can't open the file!\n");else{while((c = fgetc(fp)) != EOF){if(c == '0' || c == '1'){Test.test_mat[test_i][test_j] = c - '0';test_j++;}}}count_test++;fclose(fp);}  }_findclose(handle);                                     for (i = 0;i < count_test;i++)//计算每个test(循环中的i)数据到每个train(循环中的j)数据的距离{for (j = 0;j < count_train;j++){for (k = 0;k < LINE;k++){sum =sum + (Test.test_mat[i][k]-Train.train_mat[j][k])*(Test.test_mat[i][k]-Train.train_mat[j][k]);}mat_dist[i][j] = sqrt(sum);sum = 0;}for (l = 0;l < count_train;l++)//更新train数据的label{update_label[l] = Train.train_label[l];}classifier = BubbleSort(mat_dist[i],update_label,count_train);//调用子函数，得到第i个test数据的标签if (Test.test_label[i] != classifier)//统计错误个数{count++;}printf("the real answer is:  %d,   the classififier is:  %d\n",Test.test_label[i],classifier);//打印}rate = (float)count/count_test;//计算错误率printf("the total number of errors is:  %d\n",count);//打印printf("the total error rate is:  %f\n",rate); return 0;}

干了将近一周才把这个程序写出来，其中遇到了很多很多问题，下面做一点总结：
1、读入文件中的数据不熟悉。在读入txt文件上耗费了太多的时间。
2、对数组、指针了解太少。大数组要定义在外边作为全局就不会“太大”，数组传递以后实参也会改变。
3、对新定义的变量，能赋初值的就赋上初值。
4、杜绝编译、运行检验错误的思想，要觉得没问题了，再去编译和运行。

几个尚未解决的问题：
1、数组如何定义不会“太大”；
2、程序中读入的程序如何变成通用的子函数；
3、指针不会用；
4、找大神帮着改一下提高效率。
这些问题要解决！