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Riptide/Utils/RollingStat.cs

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+// This file is provided under The MIT License as part of RiptideNetworking.
+// Copyright (c) Tom Weiland
+// For additional information please see the included LICENSE.md file or view it on GitHub:
+// https://github.com/RiptideNetworking/Riptide/blob/main/LICENSE.md
+
+using System;
+using System.Linq;
+
+namespace Riptide.Utils
+{
+    /// <summary>Represents a rolling series of numbers.</summary>
+    public class RollingStat
+    {
+        /// <summary>The position in the array of the latest item.</summary>
+        private int index;
+        /// <summary>How many of the array's slots are in use.</summary>
+        private int slotsFilled;
+        /// <inheritdoc cref="Mean"/>
+        private double mean;
+        /// <summary>The sum of the mean subtracted from each value in the array.</summary>
+        private double sumOfSquares;
+        /// <summary>The array used to store the values.</summary>
+        private readonly double[] array;
+
+        /// <summary>The mean of the stat's values.</summary>
+        public double Mean => mean;
+        /// <summary>The variance of the stat's values.</summary>
+        public double Variance => slotsFilled > 1 ? sumOfSquares / (slotsFilled - 1) : 0;
+        /// <summary>The standard deviation of the stat's values.</summary>
+        public double StandardDev
+        {
+            get
+            {
+                double variance = Variance;
+                if (variance >= double.Epsilon)
+                {
+                    double root = Math.Sqrt(variance);
+                    return double.IsNaN(root) ? 0 : root;
+                }
+
+                return 0;
+            }
+        }
+
+        /// <summary>Initializes the stat.</summary>
+        /// <param name="sampleSize">The number of values to store.</param>
+        public RollingStat(int sampleSize)
+        {
+            index = 0;
+            slotsFilled = 0;
+            mean = 0;
+            sumOfSquares = 0;
+            array = new double[sampleSize];
+        }
+        
+        /// <summary>Adds a new value to the stat.</summary>
+        /// <param name="value">The value to add.</param>
+        public void Add(double value)
+        {
+            if (double.IsNaN(value) || double.IsInfinity(value))
+                return;
+
+            index %= array.Length;
+            double oldMean = mean;
+            double oldValue = array[index];
+            array[index] = value;
+            index++;
+
+            if (slotsFilled == array.Length)
+            {
+                double delta = value - oldValue;
+                mean += delta / slotsFilled;
+                sumOfSquares += delta * (value - mean + (oldValue - oldMean));
+            }
+            else
+            {
+                slotsFilled++;
+                double delta = value - oldMean;
+                mean += delta / slotsFilled;
+                sumOfSquares += delta * (value - mean);
+            }
+        }
+
+        /// <inheritdoc/>
+        public override string ToString()
+        {
+            if (slotsFilled == array.Length)
+                return string.Join(",", array);
+
+            return string.Join(",", array.Take(slotsFilled));
+        }
+    }
+}