From e8701195e66f2d27ffe17fb514eae8173795aaf7 Mon Sep 17 00:00:00 2001
From: Georgiy Bondarenko <69736697+nehilo@users.noreply.github.com>
Date: Thu, 4 Mar 2021 22:54:23 +0500
Subject: Initial commit

---
 Marlin/src/libs/least_squares_fit.cpp | 69 +++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 Marlin/src/libs/least_squares_fit.cpp

(limited to 'Marlin/src/libs/least_squares_fit.cpp')

diff --git a/Marlin/src/libs/least_squares_fit.cpp b/Marlin/src/libs/least_squares_fit.cpp
new file mode 100644
index 0000000..c7593c0
--- /dev/null
+++ b/Marlin/src/libs/least_squares_fit.cpp
@@ -0,0 +1,69 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2020 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 <https://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 "../inc/MarlinConfig.h"
+
+#if NEED_LSF
+
+#include "least_squares_fit.h"
+
+#include <math.h>
+
+int finish_incremental_LSF(struct linear_fit_data *lsf) {
+
+  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;
+}
+
+#endif // NEED_LSF
-- 
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