[chronojump] LeastSquares calculate maxY

[Xavier de Blas <xaviblas src gnome org>]

commit 4f0438bce1782e53543b2d0a3f74115742551057
Author: Xavier de Blas <xaviblas gmail com>
Date:   Wed Dec 11 13:19:59 2019 +0100

    LeastSquares calculate maxY

 src/utilMath.cs | 51 +++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 39 insertions(+), 12 deletions(-)
---
diff --git a/src/utilMath.cs b/src/utilMath.cs
index 4084af0e..75d1c70e 100644
--- a/src/utilMath.cs
+++ b/src/utilMath.cs
@@ -15,8 +15,8 @@
  *  along with this program; if not, write to the Free Software
  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  *
- *  Copyright (C) 2016   Xavier Padullés <x padulles gmail com> 
- *  Copyright (C) 2016-2017   Xavier de Blas <xaviblas gmail com> 
+ *  Copyright (C) 2016, 2019   Xavier Padullés <x padulles gmail com>
+ *  Copyright (C) 2016-2017, 2019   Xavier de Blas <xaviblas gmail com>
  */
 
 using System;
@@ -45,19 +45,26 @@ public class Point
 
 public class LeastSquares 
 {
-       //WIP
+       public bool CalculatedCoef;
+       public double [] Coef;  //indep, x, x^2
 
-       public bool Success;
-       public double [] Coef;
-       private List<Point> measures; 
+       /*
+        * R testing
+        * x=seq(from=min(x), to=max(x), length.out=20)
+        * plot(x, 11.51323 + 1.36524*x + -0.01752 * x^2)
+        */
 
+       public bool CalculatedMaxY;
+       public double MaxY;
+
+       //constructor
        public LeastSquares() {
                Coef = null;
        }
 
        public void Test()
        {
-               measures = new List<Point> { 
+               List<Point> measures = new List<Point> {
                        new Point(1, 10.3214), new Point(2, 13.3214), new Point(3, 18.3214),
                            new Point(4, 25.3214), new Point(5, 34.3214), new Point(6, 45.3214), 
                            new Point(7, 58.3214), new Point(8, 73.3214), new Point(9, 90.3214), new 
Point(10, 109.3214) };
@@ -66,16 +73,17 @@ public class LeastSquares
                //x=1:10
                //y=c(10.3214,13.3214,18.3214,25.3214,34.3214,45.3214,58.3214,73.3214,90.3214,109.3214)
 
-               calculate();
+               Calculate(measures);
        }
 
-       public void calculate() 
+       public void Calculate(List<Point> measures)
        {
                int numMeasures = measures.Count;
+               CalculatedCoef = false;
+               CalculatedMaxY = false;
 
                if(numMeasures < 3) {
                        LogB.Error(string.Format("LeastSquares needs at least three values, 
has:",numMeasures));
-                       Success = false;
                        return;
                }
 
@@ -122,12 +130,31 @@ public class LeastSquares
                        coef[1] = invA[1,0]*B[0] + invA[1,1]*B[1] + invA[1,2]*B[2];
                        coef[2] = invA[2,0]*B[0] + invA[2,1]*B[1] + invA[2,2]*B[2];
 
-                       Success = true;
                        Coef = coef;
+                       CalculatedCoef = true;
+
+                       calculateMaxY();
                } else {
                        LogB.Error("Determinant of matrix equal to zero");
-                       Success = false;
                }
        }
+
+       private void calculateMaxY()
+       {
+               if(Coef[2] == 0)
+               {
+                       LogB.Error("Straight line");
+                       return;
+               }
+               else if(Coef[2] > 0)
+               {
+                       LogB.Error("Inverted parabole, also solve division by zero problems");
+                       return;
+               }
+
+               //MaxY = -b / 2a
+               MaxY = - Coef[1] / (2 * Coef[2]);
+               CalculatedMaxY = true;
+       }
 }