src/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         Real x=input[i].x;
  23         Real y = input[i].y;
  24         sx += x;
  25         sy += y;
  26         sqx += sqr(x);
  27         sxy += x*y;
  28     }
  29     int N = input.size();
  30
  31
  32     coef = (N * sxy - sx*sy )/(N*sqx - sqr(sx));
  33     offset = (sy - coef * sx)/N;
  34
  35 }