bool lineFit(const std::vector &points, double &a, double &b, double &c)
{
int size = points.size();
if(size < 2)
{
a = 0;
b = 0;
c = 0;
return false;
}
double x_mean = 0;
double y_mean = 0;
for(int i = 0; i < size; i++)
{
x_mean += points[i].x;
y_mean += points[i].y;
}
x_mean /= size;
y_mean /= size; //至此，计算出了 x y 的均值 double Dxx = 0, Dxy = 0, Dyy = 0;
for(int i = 0; i < size; i++)
{
Dxx += (points[i].x - x_mean) * (points[i].x - x_mean);
Dxy += (points[i].x - x_mean) * (points[i].y - y_mean);
Dyy += (points[i].y - y_mean) * (points[i].y - y_mean);
}
double lambda = ( (Dxx + Dyy) - sqrt( (Dxx - Dyy) * (Dxx - Dyy) + 4 * Dxy * Dxy) ) / 2.0;
double den = sqrt( Dxy * Dxy + (lambda - Dxx) * (lambda - Dxx) );
if(fabs(den) < 1e-5)
{
if( fabs(Dxx / Dyy - 1) < 1e-5) //这时没有一个特殊的直线方向，无法拟合 {
return false;
}
else {
a = 1;
b = 0;
c = - x_mean;
}
}
else {
a = Dxy / den;
b = (lambda - Dxx) / den;
c = - a * x_mean - b * y_mean;
}
return true;
}
