[chronojump] Implemented CVRMSSD on force sensor variability

[Xavier de Blas <xaviblas src gnome org>]

commit f2e2ccf4a7acb216f6beee6a1380cb25bdb231dd
Author: Xavier de Blas <xaviblas gmail com>
Date:   Fri Dec 18 12:41:34 2020 +0100

    Implemented CVRMSSD on force sensor variability

 src/forceSensor.cs | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)
---
diff --git a/src/forceSensor.cs b/src/forceSensor.cs
index d476adc6..85058e94 100644
--- a/src/forceSensor.cs
+++ b/src/forceSensor.cs
@@ -952,6 +952,7 @@ public class ForceSensorCapturePoints
                double elapsedSeconds = times[countB]/1000000.0 - times[countA]/1000000.0;
                return sum * UtilAll.DivideSafe(elapsedSeconds, samples);
        }
+
        public void GetVariabilityAndAccuracy(int countA, int countB, int feedbackF, out double variability, 
out double feedbackDifference)
        {
                if(countA == countB)
@@ -961,10 +962,34 @@ public class ForceSensorCapturePoints
                        return;
                }
 
-               //calculate numSamples. Note countA and countB are included, so
+               // 1) calculate numSamples. Note countA and countB are included, so
                //countA = 2; countB = 4; samples are: 2,3,4; 3 samples
                int numSamples = (countB - countA) + 1;
 
+               // 2) get variability
+               variability = getVariabilityCVRMSSD (countA, countB, numSamples);
+
+               // 3) Calculate difference.
+               // Average of the differences between force and average
+               //feedbackDifference = Math.Abs(feedbackF - avg);
+               double sum = 0;
+               for(int i = countA; i <= countB; i ++)
+                       sum += Math.Abs(forces[i]-feedbackF);
+
+               feedbackDifference = UtilAll.DivideSafe(sum, numSamples);
+       }
+       private double getVariabilityCVRMSSD (int countA, int countB, int numSamples)
+       {
+               //Σ(x_i - x_{i+1})^2 /(n-1)  )
+               double sum = 0;
+               for(int i = countA; i < countB; i ++)
+                       sum += forces[i] - forces[i+1];
+
+               return UtilAll.DivideSafe(Math.Pow(sum, 2), numSamples -1);
+
+       }
+       private double getVariabilityOldMethod (int countA, int countB, int numSamples)
+       {
                // 1) get average
                double sum = 0;
                for(int i = countA; i <= countB; i ++)
@@ -977,17 +1002,7 @@ public class ForceSensorCapturePoints
                for(int i = countA; i <= countB; i ++)
                        sum += Math.Abs(forces[i]-avg);
 
-               variability = UtilAll.DivideSafe(sum, numSamples);
-
-               // 3) Calculate difference.
-               // Average of the differences between force and average
-
-               //feedbackDifference = Math.Abs(feedbackF - avg);
-               sum = 0;
-               for(int i = countA; i <= countB; i ++)
-                       sum += Math.Abs(forces[i]-feedbackF);
-
-               feedbackDifference = UtilAll.DivideSafe(sum, numSamples);
+               return UtilAll.DivideSafe(sum, numSamples);
        }
 
        public int MarginLeft