VarianceEvaluator.cs

using Waher.Runtime.Collections;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Model;
using Waher.Script.Objects;
using Waher.Script.Operators.Arithmetics;
 
namespace Waher.Script.Functions.Vectors
{
    public class VarianceEvaluator : UnaryIterativeEvaluator
    {
        private ChunkedList<double> doubleValues = new ChunkedList<double>();
        private ChunkedList<IElement> elementValues = null;
        private IElement sum = null;
        private double doubleSum = 0;
        private long count = 0;
        private bool isDouble = true;
 
        public VarianceEvaluator(Variance Node)
            : base(Node.Argument)
        {
        }
 
        public override void RestartEvaluator()
        {
            this.sum = null;
            this.count = 0;
            this.doubleSum = 0;
            this.isDouble = true;
 
            if (this.doubleValues is null)
                this.doubleValues = new ChunkedList<double>();
            else
                this.doubleValues.Clear();
 
            this.elementValues = null;
        }
 
        public override void AggregateElement(IElement Element)
        {
            if (this.isDouble && Element is DoubleNumber D)
            {
                this.doubleSum += D.Value;
                this.doubleValues.Add(D.Value);
            }
            else if (this.sum is null)
            {
                this.isDouble = false;
                this.elementValues = new ChunkedList<IElement>();
 
                if (this.doubleValues.Count > 0)
                {
                    ChunkNode<double> Loop = this.doubleValues.FirstChunk;
                    int i, c;
 
                    while (!(Loop is null))
                    {
                        for (i = Loop.Start, c = Loop.Pos; i < c; i++)
                            this.elementValues.Add(new DoubleNumber(Loop.Elements[i]));
 
                        Loop = Loop.Next;
                    }
                }
 
                if (this.sum is null)
                    this.sum = Element;
                else
                    this.sum = Add.EvaluateAddition(new DoubleNumber(this.doubleSum), Element, this.Node);
 
                this.elementValues.Add(Element);
            }
            else
            {
                this.sum = Add.EvaluateAddition(this.sum, Element, this.Node);
                this.elementValues.Add(Element);
            }
 
            this.count++;
        }
 
        public override IElement GetAggregatedResult()
        {
            if (this.count == 0)
                return ObjectValue.Null;
            else if (this.isDouble)
            {
                double Average = this.doubleSum / this.count;
                double Result = 0;
                double Term;
 
                ChunkNode<double> Loop = this.doubleValues.FirstChunk;
                int i, c;
 
                while (!(Loop is null))
                {
                    for (i = Loop.Start, c = Loop.Pos; i < c; i++)
                    {
                        Term = Loop[i] - Average;
                        Result += Term * Term;
                    }
 
                    Loop = Loop.Next;
                }
 
                return new DoubleNumber(Result / this.count);
            }
            else
            {
                IElement Average = Divide.EvaluateDivision(this.sum, new DoubleNumber(this.count), this.Node);
                IElement Result = null;
                IElement Term;
 
                ChunkNode<IElement> Loop = this.elementValues.FirstChunk;
                int i, c;
 
                while (!(Loop is null))
                {
                    for (i = Loop.Start, c = Loop.Pos; i < c; i++)
                    {
                        Term = Subtract.EvaluateSubtraction(Loop[i], Average, this.Node);
                        Term = Multiply.EvaluateMultiplication(Term, Term, this.Node);
 
                        if (Result is null)
                            Result = Term;
                        else
                            Result = Add.EvaluateAddition(Result, Term, this.Node);
                    }
 
                    Loop = Loop.Next;
                }
 
                if (Result is null)
                    return ObjectValue.Null;
                else
                    return Divide.EvaluateDivision(Result, new DoubleNumber(this.count), this.Node);
            }
        }
    }
}