twomul.cpp

直线型最小二乘法算法

#include <stdio.h>
#include <malloc.h>
#include <math.h>
#include<conio.h> 
struct dot
{
	float	x;
	float	y;
};
typedef	struct dot DOT;

int	getnumber(void);
void	getdata(DOT *ptrdot,int count);
void	displaydata(DOT	*ptrdot,int  count);
void	twomul(DOT *ptrdot,int count,float *k,float *b,float *r);



void main()
{

	float	k=0.0,b=0.0,r=0.0;
	int	N=0;
	char	sel='q';
	DOT	*ptrdot;
	printf("////////////////////////////////////////////////////////////////////////////////");
do
{
	N=getnumber();
	ptrdot=(DOT *)malloc(N*sizeof(DOT));
	if(ptrdot==NULL)
	{
		printf("memory in short! press any key to end...");
		getch();
	}


	getdata(ptrdot,N);

	displaydata(ptrdot,N);

	twomul(ptrdot,N,&k,&b,&r);

	printf("\nk = %-8.6f\tb = %-8.6f\tr = %-8.6f\n",k,b,r);

	printf("press q/Q to exit,else to continue...");
	free(ptrdot);
	sel=getch();
	printf("\n///////////////////////////////////////////////////////////////////////////////\n");
}while((sel!='q')&&(sel!='Q'));
}
int	getnumber(void)
{
	int n=0;
	printf("please input count of valuable dots: ");
	do
	{
		scanf("%d",&n);
		n=(int)n;
		if(n<2){printf("count too small! please retry...");}
		if(n>100){printf("count too large! please retry...");}
	}while(n<2 || n>100);

	return	n;
}

void	getdata(DOT *ptrdot,int count)
{
	float	tempx=0.0,tempy=0.0;
	int	i=0;
		printf("\ninput dot: X Y\n");
	while(i<count)
	{
		printf("please input dot %d :",i+1);
		scanf("%f%f",&tempx,&tempy);
		(ptrdot+i)->x = tempx;
		(ptrdot+i)->y = tempy;
		i++;
	};
}
void	displaydata(DOT	*ptrdot,int  count)
{
	int	i=0;
	printf("\ndata you have input:\n");
	while(i<count)
	{
		printf("dot%d:(%f,%f)\n",i+1,(ptrdot+i)->x,(ptrdot+i)->y);
		i++;
	};
	printf("\n");
}
void	twomul(DOT *ptrdot,int count,float *k,float *b,float *r)
{
	float	tempx=0.0,tempy=0.0;
	float	ave_x=0.0,ave_y=0.0,ave_xy=0.0,ave_x2=0.0,ave_y2=0.0;

	int	i=0;

	while(i<count)
	{
		tempx=(ptrdot + i)->x;
		tempy=(ptrdot + i)->y;
		ave_x += tempx;
		ave_y += tempy;
		ave_xy +=(tempx*tempy);
		ave_x2 +=(pow(tempx,2));
		ave_y2 +=(pow(tempy,2));
		i++;
	};
		ave_x /= count;
		ave_y /= count;
		ave_xy /= count;
		ave_x2 /= count;
		ave_y2 /= count;
	printf("ave_x  = %-8.6f\tave_y  = %-8.6f\nave_x2 = %-8.6f\tave_y2 = %-8.6f\nave_xy = %-8.6f\n",ave_x,ave_y,ave_x2,ave_y2,ave_xy);
	*k=(ave_x * ave_y - ave_xy)/(ave_x * ave_x - ave_x2);
	*b=ave_y - (*k)*ave_x;
	*r=(ave_xy - ave_x * ave_y)/(sqrt((ave_x2 -pow(ave_x,2))*(ave_y2 - pow(ave_y,2))));
}