模式识别

贝叶斯最小错误率决策（C实现）

/*
 *Author:Lu Daze
 *Last modified time: Feb 4th, 2021
 *Function: Bayesian minimum wrong decision
 */

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
    // the number of classes
    int n_class;
    // The index of max number
    int in_d;
    // denominator
    double denominator=0.0;
    
    // apply a one dimensional array for these classes
    printf("How many classes can wo choose?\n");
    scanf("%d",&n_class);
    double *prior_p,*Den_f,*molecure,*result,*cresult;
    prior_p=(double *)calloc(n_class,sizeof(double));
    //class conditional probability density function
    Den_f=(double *)calloc(n_class,sizeof(double));
    // molecure
    molecure=(double *)calloc(n_class,sizeof(double));
    // The result of caculation
    result=(double *)calloc(n_class,sizeof(double));
    // to copy result
    cresult=(double *)calloc(n_class,sizeof(double));
    // the prior probability of classes
    printf("Enter the prior paobability of the classes:\n");
    for (int i=0;i<n_class;i++)
        scanf("%lf",&prior_p[i]);

    printf("Enter the %d  class conditional probability density functions please:\n",n_class);
    for (int i=0;i<n_class;i++)
        scanf("%lf",&Den_f[i]);
   
    for (int i=0;i<n_class;i++)
        molecure[i]=Den_f[i]*prior_p[i];

    // caculate denominator
    for (int i=0;i<n_class;i++)
        denominator+=molecure[i];

    // The result of caculation
    for (int i=0;i<n_class;i++)
        result[i]=molecure[i]/denominator;
    // copy result before sort, wihch is used to find the max number's index
    cresult=result;
    // display the result
    printf("The result are:\n");
    for (int i=0;i<n_class;i++)
        printf("%lf  ",result[i]);
    printf("\n");
    //compare all the results, find the last one
    for (int i=0;i<n_class-1;i++)
    {
        if (result[i]>result[i+1])
        {
            double min=result[i+1];
            result[i+1]=result[i];
            result[i]=min;
        }
    }

    // Find the index
    for (int i=0;i<n_class;i++)
    {
        if (cresult[i]==result[n_class])
        {
            //index
            in_d=i;
            break;
        }
        else
            continue;
    }
    printf("The object belongs to class %d!\n",in_d+1);
    free(prior_p);
    free(Den_f);
    free(molecure);
    free(result);
    //free(cresult);
    printf("The danamic array prior_p, Den_f, result, molecure, cresult have been released!\n");
    return 0;
}