Chi.cs

using System;
using System.Text;
using System.Threading.Tasks;
using System.Xml;
using Waher.Content;
using Waher.Content.Xml;
using Waher.Script.Statistics;
 
namespace TAG.Simulator.ObjectModel.Distributions
{
    public class Chi : Distribution
    {
        protected double t0;
 
        protected double k;
 
        protected double kHalf;
 
        protected double c;
 
        public Chi(ISimulationNode Parent, Model Model)
            : base(Parent, Model)
        {
        }
 
        public override string LocalName => nameof(Chi);
 
        public override ISimulationNode Create(ISimulationNode Parent, Model Model)
        {
            return new Chi(Parent, Model);
        }
 
        public override Task FromXml(XmlElement Definition)
        {
            this.t0 = XML.Attribute(Definition, "t0", 0.0);
            this.k = XML.Attribute(Definition, "k", 0.0);
 
            this.kHalf = this.k / 2;
            this.c = 1.0 / StatMath.Γ(this.kHalf);
 
            return base.FromXml(Definition);
        }
 
        protected override double GetCumulativeProbability(double t, int NrCycles)
        {
            t -= this.t0;
            if (t < 0)
                return 0;
            else
                return StatMath.γ(this.kHalf, t * t / 2) * this.c;
        }
 
        public override void ExportPdfBody(StringBuilder Output)
        {
            Output.Append("t<");
            Output.Append(CommonTypes.Encode(this.t0));
            Output.Append("?0:");
            Output.Append(CommonTypes.Encode(this.c * Math.Pow(2, 1 - this.kHalf)));
            Output.Append("*(t-");
            Output.Append(CommonTypes.Encode(this.t0));
            Output.Append(").^");
            Output.Append(CommonTypes.Encode(this.k - 1));
            Output.Append(".*exp(-(t-");
            Output.Append(CommonTypes.Encode(this.t0));
            Output.Append(").^2/2)");
        }
    }
}