lily/leastsquares.cc

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