Variance.cs

using System.Numerics;
using Waher.Script.Abstraction.Elements;
using Waher.Script.Exceptions;
using Waher.Script.Model;
using Waher.Script.Objects;
using Waher.Script.Objects.VectorSpaces;
 
namespace Waher.Script.Functions.Vectors
{
    public class Variance : FunctionOneVectorVariable, IIterativeEvaluation
    {
        public Variance(ScriptNode Argument, int Start, int Length, Expression Expression)
            : base(Argument, Start, Length, Expression)
        {
        }
 
        public override string FunctionName => nameof(Variance);
 
        public override string[] Aliases => new string[] { "var" };
 
        public override IElement EvaluateVector(DoubleVector Argument, Variables Variables)
        {
            return new DoubleNumber(CalcVariance(Argument.Values, this));
        }
 
        public static double CalcVariance(double[] Values, ScriptNode Node)
        {
            double Avg = Average.CalcAverage(Values, Node);
            double Result = 0;
            double d;
            int i, c = Values.Length;
 
            for (i = 0; i < c; i++)
            {
                d = (Values[i] - Avg);
                Result += d * d;
            }
 
            Result /= c;
 
            return Result;
        }
 
        public override IElement EvaluateVector(ComplexVector Argument, Variables Variables)
        {
            return new ComplexNumber(CalcVariance(Argument.Values, this));
        }
 
        public static Complex CalcVariance(Complex[] Values, ScriptNode Node)
        {
            Complex Avg = Average.CalcAverage(Values, Node);
            Complex Result = 0;
            Complex d;
            int i, c = Values.Length;
 
            for (i = 0; i < c; i++)
            {
                d = (Values[i] - Avg);
                Result += d * d;
            }
 
            Result /= c;
 
            return Result;
        }
 
        public override IElement EvaluateVector(IVector Argument, Variables Variables)
        {
            throw new ScriptRuntimeException("Expected a numeric vector.", this);
        }
 
        public override IIterativeEvaluator CreateEvaluator() => new VarianceEvaluator(this);
    }
}