C#与Minitab：合并标准差Sigma计算

using MathNet.Numerics.Statistics;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Spc.Core
{
    /// <summary>
    /// 合并标准差方法
    /// </summary>
    public class PooledEstimateSigma : IEstimateSigma
    {
        public double GetSigma(double[] vs, bool useUnbiasedConstant = false, int sampleSize = 0, int movingRangeLength = 2)
        {
            var sp = 0d;
            var n = 0;
            if (sampleSize <= 0)
            {
                n = 2;
            }
            else
            {
                n = sampleSize;
            }
            sp = vs.Average();

            if (useUnbiasedConstant)
            {
                var d = vs.Sum(x => n - 1);
                var c4 = SigmaConstants.C4AddOne(d);
                sp = sp.Div(c4);
            }
            return sp;
        }

        public double GetSigma(double[][] vs, bool useUnbiasedConstant = false, int sampleSize = 0, int movingRangeLength = 2)
        {
            var sp = 0d;
            var counts = vs.Select(m => m.Length).ToArray();
            if (counts.Min() != counts.Max())
            {
                var sn = vs.Sum(x => Math.Pow(x.Sum(x1 => x1.Sub(x.Average())), 2));
                var ni = vs.Sum(x => x.Length - 1);
                sp = Math.Sqrt(sn.Div(ni));
            }
            else
            {
                sp = vs.Average(x => Statistics.StandardDeviation(x));
            }

            if (useUnbiasedConstant)
            {
                var d = vs.Sum(x => x.Length - 1);
                var c4 = SigmaConstants.C4(d + 1);
                sp = sp.Div(c4);
            }
            return sp;
        }
    }
}