/**
* 说明：5阶最小二乘法函数接口
* x：x坐标值
* y：y坐标值
* num：点的个数
* a,b,c,d,e,f ：拟合系数
* y = ax5 + bx4 + cx3 + dx2 + ex + f
*/
void Fit5(double *x, double *y, const int num,
double *a, double *b, double *c, double *d, double *e, double *f)
{
double sum_x = 0;
double sum_x2 = 0;
double sum_x3 = 0;
double sum_x4 = 0;
double sum_x5 = 0;
double sum_x6 = 0;
double sum_x7 = 0;
double sum_x8 = 0;
double sum_x9 = 0;
double sum_x10 = 0;
double sum_y = 0;
double sum_xy = 0;
double sum_x2y = 0;
double sum_x3y = 0;
double sum_x4y = 0;
double sum_x5y = 0;
for (int i = 0; i < num; ++i)
{
sum_x += x[i];
sum_x2 += x[i] * x[i];
sum_x3 += x[i] * x[i] * x[i];
sum_x4 += x[i] * x[i] * x[i] * x[i];
sum_x5 += x[i] * x[i] * x[i] * x[i] * x[i];
sum_x6 += x[i] * x[i] * x[i] * x[i] * x[i] * x[i];
sum_x7 += x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i];
sum_x8 += x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i];
sum_x9 += x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i];
sum_x10 += x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i] * x[i];
sum_y += y[i];
sum_xy += x[i] * y[i];
sum_x2y += x[i] * x[i] * y[i];
sum_x3y += x[i] * x[i] * x[i] * y[i];
sum_x4y += x[i] * x[i] * x[i] * x[i] * y[i];
sum_x5y += x[i] * x[i] * x[i] * x[i] * x[i] * y[i];
}
sum_x /= num;
sum_x2 /= num;
sum_x3 /= num;
sum_x4 /= num;
sum_x5 /= num;
sum_x6 /= num;
sum_x7 /= num;
sum_x8 /= num;
sum_x9 /= num;
sum_x10 /= num;
sum_y /= num;
sum_xy /= num;
