[chronojump] method to calculateY based on calculated proportion of any variable on cairo XY graphs

[Xavier de Blas <xaviblas src gnome org>]

commit 33ed03479108bbcefa802dec684574ee3d4929b9
Author: Xavier de Blas <xaviblas gmail com>
Date:   Mon May 9 17:58:03 2022 +0200

    method to calculateY based on calculated proportion of any variable on cairo XY graphs

 src/gui/cairo/xy.cs | 6 ++++++
 src/utilMath.cs     | 9 +++++++++
 2 files changed, 15 insertions(+)
---
diff --git a/src/gui/cairo/xy.cs b/src/gui/cairo/xy.cs
index fe154a185..467ebbf22 100644
--- a/src/gui/cairo/xy.cs
+++ b/src/gui/cairo/xy.cs
@@ -679,6 +679,12 @@ public abstract class CairoXY : CairoGeneric
                                absoluteMaxY - minY));
         }
 
+       //when you want to plot another value, so minY, maxY is different
+       protected double calculatePaintYProportion (double YProp) //from 0 to 1
+       {
+                return graphHeight - totalMargins - (YProp * (graphHeight - 2*totalMargins));
+       }
+
        // Fast calculatePaintX/Y, sadly for 10000 points the difference between fast and slow is very low
 
        /*
diff --git a/src/utilMath.cs b/src/utilMath.cs
index a98c49b0c..c754e36c1 100644
--- a/src/utilMath.cs
+++ b/src/utilMath.cs
@@ -624,6 +624,15 @@ public static class MathUtil
                return min;
        }
 
+       public static double GetProportion (double d, List<double> d_l)
+       {
+               double max = GetMax (d_l);
+               double min = GetMin (d_l);
+
+               d -= min; //move d to 0
+               return UtilAll.DivideSafe(d, max - min);
+       }
+
 }
 
 public class InterpolateSignal