[chronojump] Force sensor: Nicer code for GetVariabilityAndAccuracy

[Xavier de Blas <xaviblas src gnome org>]

commit e7c7100e2579384f1fccc2a8fb3c2e537929f560
Author: Xavier de Blas <xaviblas gmail com>
Date:   Fri Jun 7 14:39:51 2019 +0200

    Force sensor: Nicer code for GetVariabilityAndAccuracy

 src/forceSensor.cs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/src/forceSensor.cs b/src/forceSensor.cs
index 8ef65f92..ea024d8c 100644
--- a/src/forceSensor.cs
+++ b/src/forceSensor.cs
@@ -256,13 +256,17 @@ public class ForceSensorCapturePoints
                        return;
                }
 
+               //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;
+
                // 1) get average
                double sum = 0;
                for(int i = countA; i <= countB; i ++)
                        sum += forces[i];
 
 
-               double avg = sum / ((countB - countA) +1);
+               double avg = sum / numSamples;
 
                // 2) move all the forces to 0 (substracting from average)
                //    and have them in absolute value
@@ -270,7 +274,7 @@ public class ForceSensorCapturePoints
                for(int i = countA; i <= countB; i ++)
                        sumAt0 += Math.Abs(forces[i]-avg);
 
-               variability = Util.DivideSafe(sumAt0, ((countB - countA) +1));
+               variability = Util.DivideSafe(sumAt0, numSamples);
                feedbackDifference = Math.Abs(feedbackN - avg);
        }