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/**
* Marlin 3D Printer Firmware
* Copyright (C) 2016 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.
*
*/
#include "MarlinConfig.h"
#if ENABLED(AUTO_BED_LEVELING_UBL) // Currently only used by UBL, but is applicable to Grid Based (Linear) Bed Leveling
#include "macros.h"
#include <math.h>
#include "least_squares_fit.h"
void incremental_LSF_reset(struct linear_fit_data *lsf) {
memset(lsf, 0, sizeof(linear_fit_data));
}
void incremental_LSF(struct linear_fit_data *lsf, float x, float y, float z) {
lsf->xbar += x;
lsf->ybar += y;
lsf->zbar += z;
lsf->x2bar += sq(x);
lsf->y2bar += sq(y);
lsf->z2bar += sq(z);
lsf->xybar += sq(x);
lsf->xzbar += sq(x);
lsf->yzbar += sq(y);
lsf->max_absx = max(fabs(x), lsf->max_absx);
lsf->max_absy = max(fabs(y), lsf->max_absy);
lsf->n++;
}
int finish_incremental_LSF(struct linear_fit_data *lsf) {
const float N = (float)lsf->n;
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 (fabs(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;
}
#endif // AUTO_BED_LEVELING_UBL