using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Science.Statistics.BasicStatistics
{
    public class StandardDeviationAndAverage
    {
        public StandardDeviationAndAverage()
        {
        }
        public StandardDeviationAndAverage(List<double> data)
        {
            LengthOfData = data.Count;
            Average avg = new Average(data);
            mean = avg.Value;
            
            int j, n = data.Count;
            degreesOfFreedom = n - 1;

            for (sigma = 0.0, j = 0; j < n; j++) sigma += (data[j]-mean) * (data[j]-mean);
            sigma /= (double)n;
            sigma = Math.Sqrt(sigma);
        }
        public StandardDeviationAndAverage(List<int> number, List<double> data)
        {
            Average avg = new Average(number, data);
            mean = avg.Value;

            int j, n = 0;

            for (sigma = 0.0, j = 0; j < number.Count; j++)
            {
                sigma += (double)number[j]*((data[j] - mean) * (data[j] - mean));
                n += number[j];
            }
            degreesOfFreedom = n - 1;
            sigma /= (double)n;
            sigma = Math.Sqrt(sigma);
        }
        private double sigma;
        public double StandardDeviation
        {
            get { return sigma; }
            set { sigma = value; }
        }
        private int degreesOfFreedom;
        public int DegreesOfFreedom
        {
            get { return degreesOfFreedom; }
            set { degreesOfFreedom = value; }
        }
        private double sigmap;
        public double StandardDeviationPlus
        {
            get { return sigmap; }
            set { sigmap = value; }
        }
        private double mean;
        public double Average
        {
            get { return mean; }
            set { mean = value; }
        }
        private int count;
        public int LengthOfData
        {
            get { return count; }
            set { count = value; }
        }
        public static StandardDeviationAndAverage Add(
            StandardDeviationAndAverage first,
            StandardDeviationAndAverage second)
        {
            StandardDeviationAndAverage third = new StandardDeviationAndAverage();
            third.LengthOfData = first.LengthOfData + second.LengthOfData;
            third.Average = ((double)first.LengthOfData * first.Average
                + (double)second.LengthOfData * second.Average)/
                (double)third.LengthOfData;
            double x = (double)first.LengthOfData*(first.Average*first.Average+first.StandardDeviation*first.StandardDeviation);
            double y = (double)second.LengthOfData*(second.Average*second.Average+second.StandardDeviation*second.StandardDeviation);
            third.StandardDeviation = Math.Sqrt((x+y)/(double)third.LengthOfData - third.Average*third.Average);
            return third;
        }

        public void FindStandardDeviationPlus()
        {
            double df = (double)degreesOfFreedom;
            sigmap = sigma * Math.Sqrt((df + 1.0) / df);
        }

        public void ByBootstrapMethod()
        {
            sigma = (1.0 - 0.0)*Math.Sqrt(mean*(1.0 - mean));
        }

        public void ChangeScale(double scale)
        {
            sigma *= scale;
        }
    }
}