least_squares_fit.cpp File Reference

#include "../inc/MarlinConfig.h"
#include "least_squares_fit.h"
#include <math.h>

Functions
int	finish_incremental_LSF (struct linear_fit_data *lsf)

Function Documentation

finish_incremental_LSF()

int finish_incremental_LSF

(

struct linear_fit_data *

lsf

)

Marlin 3D Printer Firmware Copyright (c) 2019 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]

Based on Sprinter and grbl. Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm

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 3 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, see http://www.gnu.org/licenses/. Least Squares Best Fit by Roxy and Ed Williams

This algorithm is high speed and has a very small code footprint. Its results are identical to both the Iterative Least-Squares published earlier by Roxy and the QR_SOLVE solution. If used in place of QR_SOLVE it saves roughly 10K of program memory. It also does not require all of coordinates to be present during the calculations. Each point can be probed and then discarded.

                                                        {
 
  const float N = lsf->N;
 
  if (N == 0.0)
    return 1;
 
  lsf->xbar /= N;
  lsf->ybar /= N;
  lsf->zbar /= N;
  lsf->x2bar = lsf->x2bar / N - sq(lsf->xbar);
  lsf->y2bar = lsf->y2bar / N - sq(lsf->ybar);
  lsf->z2bar = lsf->z2bar / N - sq(lsf->zbar);
  lsf->xybar = lsf->xybar / N - lsf->xbar * lsf->ybar;
  lsf->yzbar = lsf->yzbar / N - lsf->ybar * lsf->zbar;
  lsf->xzbar = lsf->xzbar / N - lsf->xbar * lsf->zbar;
  const float DD = lsf->x2bar * lsf->y2bar - sq(lsf->xybar);
 
  if (ABS(DD) <= 1e-10 * (lsf->max_absx + lsf->max_absy))
    return 1;
 
  lsf->A = (lsf->yzbar * lsf->xybar - lsf->xzbar * lsf->y2bar) / DD;
  lsf->B = (lsf->xzbar * lsf->xybar - lsf->yzbar * lsf->x2bar) / DD;
  lsf->D = -(lsf->zbar + lsf->A * lsf->xbar + lsf->B * lsf->ybar);
  return 0;
}