luatos-soc-air101/platform/drivers/adc/wm_polyfit.c

/*Functtion :多项式拟合polyfit
**********************************************/
#include <stdio.h>
//#include <conio.h>
#include <stdlib.h>
#include <math.h>
#include "wm_mem.h"

void polyfit_verify(double x, double* a)
{
	double y1 = a[1]*x + a[0];
	printf("x=%d, y1=%d\n", (int)x, (int)(y1+0.5));
}


/*==================polyfit(n,x,y,poly_n,a)===================*/
/*=======拟合y=a0+a1*x+a2*x^2+……+apoly_n*x^poly_n========*/
/*=====n是数据个数 xy是数据值 poly_n是多项式的项数======*/
/*===返回a0,a1,a2,……a[poly_n]，系数比项数多一（常数项）=====*/
void polyfit(int n,double x[],double y[],int poly_n,double a[])
{
int i,j;
double *tempx,*tempy,*sumxx,*sumxy,*ata;
void gauss_solve(int n,double A[],double x[],double b[]);
tempx=tls_mem_calloc(n,sizeof(double));
sumxx=tls_mem_calloc(poly_n*2+1,sizeof(double));
tempy=tls_mem_calloc(n,sizeof(double));
sumxy=tls_mem_calloc(poly_n+1,sizeof(double));
ata=tls_mem_calloc((poly_n+1)*(poly_n+1),sizeof(double));
for (i=0;i<n;i++)
     {
      tempx[i]=1;
      tempy[i]=y[i];
     }
for (i=0;i<2*poly_n+1;i++)
     for (sumxx[i]=0,j=0;j<n;j++)
   {
    sumxx[i]+=tempx[j];
    tempx[j]*=x[j];
   }
for (i=0;i<poly_n+1;i++)
    for (sumxy[i]=0,j=0;j<n;j++)
   {
    sumxy[i]+=tempy[j];
    tempy[j]*=x[j];
   }
for (i=0;i<poly_n+1;i++)
     for (j=0;j<poly_n+1;j++)
ata[i*(poly_n+1)+j]=sumxx[i+j];
gauss_solve(poly_n+1,ata,a,sumxy);

tls_mem_free(tempx);
tls_mem_free(sumxx);
tls_mem_free(tempy);
tls_mem_free(sumxy);
tls_mem_free(ata);
}

void gauss_solve(int n,double A[],double x[],double b[])
{
int i,j,k,r;
double max;
for (k=0;k<n-1;k++)
     {
      max=fabs(A[k*n+k]); /*find maxmum*/
      r=k;
      for (i=k+1;i<n-1;i++)
   if (max<fabs(A[i*n+i]))
      {
       max=fabs(A[i*n+i]);
       r=i;
      }
      if (r!=k)
for (i=0;i<n;i++)         /*change array:A[k]&A[r] */
      {
       max=A[k*n+i];
       A[k*n+i]=A[r*n+i];
       A[r*n+i]=max;
      }
      max=b[k];                    /*change array:b[k]&b[r]     */
      b[k]=b[r];
      b[r]=max;
      for (i=k+1;i<n;i++)
   {
    for (j=k+1;j<n;j++)
        A[i*n+j]-=A[i*n+k]*A[k*n+j]/A[k*n+k];
    b[i]-=A[i*n+k]*b[k]/A[k*n+k];
   }
     }

for (i=n-1;i>=0;x[i]/=A[i*n+i],i--)
     for (j=i+1,x[i]=b[i];j<n;j++)
x[i]-=A[i*n+j]*x[j];
}

void polyfit_test(void)
{
	int i,n=2,poly_n=1;
	double x[2]={15174, 19196},y[2]={5000, 9986};
	double a[2];
	void polyfit(int n,double *x,double *y,int poly_n,double a[]);


	polyfit(n,x,y,poly_n,a);

	for (i=0;i<poly_n+1;i++)/*这里是升序排列，Matlab是降序排列*/
	     printf("a[%d]=%lf \n",i,a[i]);

	for(i = 0; i < n; i++)
	{
		polyfit_verify(x[i], a);
	}
}