Simple BS average replaced with weighted average

Author: bosik

portable/comp-android/diacomp/src/main/java/org/bosik/diacomp/android/frontend/fragments/FragmentTabCharts.java

@@ -46,6 +46,7 @@
 import org.bosik.diacomp.core.entities.business.diary.records.MealRecord;
 import org.bosik.diacomp.core.services.analyze.RateService;
 import org.bosik.diacomp.core.services.analyze.entities.Rate;
+import org.bosik.diacomp.core.services.analyze.entities.WeightedValue;
 import org.bosik.diacomp.core.services.diary.DiaryService;
 import org.bosik.diacomp.core.utils.Utils;
 import org.bosik.merklesync.Versioned;
@@ -176,10 +177,25 @@ public Collection<Series<?>> load(Context context)
 
 					if (!items.isEmpty())
 					{
-						Collection<Double> values = items.values();
+						final List<Date> keys = new ArrayList<>(items.keySet());
+						final List<WeightedValue> points = new ArrayList<>();
+
+						if (keys.size() == 1)
+						{
+							points.add(new WeightedValue(items.get(keys.get(0)), 1.0));
+						}
+						else
+						{
+							for (int j = 0; j < keys.size() - 1; j++)
+							{
+								final double value = (items.get(keys.get(j)) + items.get(keys.get(j + 1))) / 2;
+								final double weight = keys.get(j + 1).getTime() - keys.get(j).getTime();
+								points.add(new WeightedValue(value, weight));
+							}
+						}
 
-						double mean = Utils.getMean(values);
-						double deviation = Utils.getDeviation(values, mean);
+						double mean = Utils.getWeightedMean(points);
+						double deviation = Utils.getWeightedDeviation(points, mean);
 						dataAvg.add(new DataPoint(windowMiddle, mean));
 						dataMin.add(new DataPoint(windowMiddle, mean - deviation));
 						dataMax.add(new DataPoint(windowMiddle, mean + deviation));

portable/comp-transfer/src/main/java/org/bosik/diacomp/core/services/analyze/entities/WeightedValue.java

@@ -0,0 +1,54 @@
+/*
+ * Diacomp - Diabetes analysis & management system
+ * Copyright (C) 2025 Nikita Bosik
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+package org.bosik.diacomp.core.services.analyze.entities;
+
+public class WeightedValue
+{
+	private double value;
+	private double weight;
+
+	public WeightedValue()
+	{
+	}
+
+	public WeightedValue(double value, double weight)
+	{
+		this.value = value;
+		this.weight = weight;
+	}
+
+	public double getValue()
+	{
+		return value;
+	}
+
+	public void setValue(double value)
+	{
+		this.value = value;
+	}
+
+	public double getWeight()
+	{
+		return weight;
+	}
+
+	public void setWeight(double weight)
+	{
+		this.weight = weight;
+	}
+}

portable/comp-transfer/src/main/java/org/bosik/diacomp/core/utils/Utils.java

@@ -19,6 +19,7 @@
 
 import org.bosik.diacomp.core.entities.business.Units;
 import org.bosik.diacomp.core.services.analyze.entities.Rate;
+import org.bosik.diacomp.core.services.analyze.entities.WeightedValue;
 import org.bosik.diacomp.core.services.preferences.PreferenceID;
 import org.json.JSONArray;
 
@@ -764,6 +765,27 @@ public static double getMean(Collection<Double> values)
 		}
 	}
 
+	public static double getWeightedMean(Collection<WeightedValue> values)
+	{
+		double totalValue = 0.0;
+		double totalWeight = 0.0;
+
+		for (WeightedValue x : values)
+		{
+			totalValue += x.getValue() * x.getWeight();
+			totalWeight += x.getWeight();
+		}
+
+		if (totalWeight > 0)
+		{
+			return totalValue / totalWeight;
+		}
+		else
+		{
+			return 0.0;
+		}
+	}
+
 	/**
 	 * Calculates standard deviation using pre-calculated mean
 	 *
@@ -787,6 +809,28 @@ public static double getDeviation(Collection<Double> values, double mean)
 		return Math.sqrt(s);
 	}
 
+	public static double getWeightedDeviation(Collection<WeightedValue> values, double mean)
+	{
+		double totalValue = 0.0;
+		double totalWeight = 0.0;
+
+		for (WeightedValue x : values)
+		{
+			final double centered = x.getValue() - mean;
+			totalValue += centered * centered * x.getWeight();
+			totalWeight += x.getWeight();
+		}
+
+		if (totalWeight > 0)
+		{
+			return Math.sqrt(totalValue / totalWeight);
+		}
+		else
+		{
+			return 0.0;
+		}
+	}
+
 	/* =========================================================================================
 	 * RANDOM
 	 * =========================================================================================/