/* leastsqs.h -- Implements a simple linear least squares best fit routine
 *
 * Written by Curtis Olson, started September 1997.
 *
 * Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id$
 * (Log is kept at end of this file)
 */


/* 
Least squares fit:

y = b0 + b1x

     n*sum(xi*yi) - (sum(xi)*sum(yi))
b1 = --------------------------------
     n*sum(xi^2) - (sum(xi))^2


b0 = sum(yi)/n - b1*(sum(xi)/n)
*/

void least_squares(double *x, double *y, int n, double *m, double *b);


/* 
  return the least squares error:

              (y[i] - y_hat[i])^2
              -------------------
                      n
 */
double least_squares_error(double *x, double *y, int n, double m, double b);


/* 
  return the maximum least squares error:

              (y[i] - y_hat[i])^2
 */
double least_squares_max_error(double *x, double *y, int n, double m, double b);


/* $Log$
/* Revision 1.1  1998/03/19 02:54:48  curt
/* Reorganized into a class lib called fgDEM.
/*
 * Revision 1.1  1997/10/13 17:02:35  curt
 * Initial revision.
 *
 */