#include <string.h>
#include<math.h>
int main()//是少了main函数,程序里面一定要有main函数的
{
double p[100]//每个信源的概率
int n//信源个数
int i
double sum=0
scanf("%d",&n)
for(i=0i<ni++)
{
scanf("%lf",&p[i])
sum+=-p[i]*(log(p[i])/log(2.0))
}
printf("%lf\n",sum)
return 0
}
1、熵是描述区域的随机程度的,P=ΣC*logC,C是灰度概率值,当图像均匀时,各灰度值的概率基本相等,熵可以达到最大
2、例程:
#include<iostream.h>#include<math.h>
int i,j
double rowsum(double table[][4],int nrow)//定义第i行的边际概率函数
{
for(i=0i<nrowi++)
{
for( j=1j<4j++)
table[i][0]+=table[i][j]
}
return 0
}
double liesum(double table[4][4],int nlie)//定义第j列的边际概率函数
{ for( j=0j<nliej++)
{
for( i=1i<4i++)
table[0][j]+=table[i][j]
}
return 0
}
void main()
{
double p[4][4]={{1.0/8.0,1.0/16.0,1.0/32.0,1.0/32.0},{1.0/16.0,1.0/8.0,1.0/32.0,1.0/32.0},
{1.0/16.0,1.0/16.0,1.0/16.0,1.0/16.0},{1.0/4.0,0.0,0.0,0.0}}
for ( i=0i<4i++)//输出概率矩阵
{
for ( j=0j<4j++)
cout<<p[i][j]<<" "
cout<<endl
}cout<<endl
rowsum(p,4)//调用函数输出第i行的边际概率
for (i =0i<4i++)
{cout<<"第"<<i<<"行的边际概率p"<<"["<<i<<"]"<<"是"<<p[i][0]<<endl}cout<<endl
liesum(p,4)//调用函数输出第j列的边际概率
for ( j =0j<4j++)
{cout<<"第"<<j<<"列的条件概率p"<<"["<<j<<"]"<<"是"<<p[0][j]<<endl}cout<<endl
// double p[4][4]
double H1=0.0
for( i=0i<4i++)
{H1+=p[i][0]*(log((1.0/p[i][0])/log(2.0)))}
double H2=0.0
for( j=0j<4j++)
{H2+=p[0][j]*(log((1.0/p[0][j])/log(2.0)))}
double H3=0.0
for(i=0i<3i++)
for(j=0j<4j++)
{H3+=p[i][j]*(log(1.0/p[i][j])/log(2.0))}
H3+=p[4][1]*(log(1.0/p[4][1])/log(2.0))
cout<<"X的熵:H(X)="<<H1<<endl
cout<<"Y的熵:H(Y)="<<H2<<endl
cout<<"(X,Y)的熵:H(X,Y)="<<H3<<endl
cout<<endl
cout<<"条件熵:H(X|Y)="<<H3-H2<<endl
cout<<"条件熵:H(Y|X)="<<H3-H1<<endl
cout<<"互信息:I(XY)="<<H1+H2-H3<<endl
int size=4//定义联合概率p为维数组
double *p
p=new double[size]
for ( i=0i<4i++)//联合概率计算
{
for ( j=0j<4j++)
{
/*int nSize
scanf( "%d", &nSize )
int *p = ( int* )malloc( sizeof( int ) * nSize )
for( int i = 0 i < nSize i++ )
p[ i ] = 0
double table[4][4]
p[i]=pp[0][i]*table[i][j]
cout<<"联合概率"<<"p"<<"["<<i<<"]"<<"["<<j<<"]""是"<<p[i]<<endl
}
}
for ( i=0i<4i++)//联合熵的计算
{
for ( j=0j<4j++)
{
// H+=p[i][j]*log(1.0/p[i][j])
H+=p[i]*(log((1.0/p[i])/log(2.0)))
}
}
cout<<"联合H(x,y)熵为"<<H<<endl
delete []p */
}