lily/leastsquares.cc

   1 #include "leastsquares.hh"
   2
   3 void
   4 Least_squares::OK() const
   5 {
   6   assert (input.size() > 1);
   7   Real dx = 0.0;
   8   for (int i=1; i < input.size(); i++)
   9         dx += abs (input[i-1].x() - input[i].x ());
  10
  11   assert (dx);
  12 }
  13
  14 void
  15 Least_squares::minimise (Real &coef, Real &offset)
  16 {
  17   OK();
  18   Real sx = 0.0;
  19   Real sy = 0.0;
  20   Real sqx =0.0;
  21   Real sxy = 0.0;
  22
  23   for (int i=0; i < input.size();i++)
  24     {
  25         Real x=input[i].x();
  26         Real y = input[i].y();
  27         sx += x;
  28         sy += y;
  29         sqx += sqr (x);
  30         sxy += x*y;
  31     }
  32   int N = input.size();
  33
  34
  35   coef = (N * sxy - sx*sy)/(N*sqx - sqr (sx));
  36   offset = (sy - coef * sx)/N;
  37
  38 }