拉依达准则 剔除异常点

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

namespace Tool
{
	/// <summary>
	/// 拉依达准则 剔除异常数据
	/// </summary>
	public class Laida
	{
		/// <summary>
		/// 初始化?
		/// </summary>
		public Laida()
		{
		}


		/// <summary>
		/// 平均值
		/// </summary>
		/// <returns></returns>
		static double SetMean<T>(IList<T> list, double sum)
		{
			return sum / list.Count;
		}


		/// <summary>
		/// 标准差
		/// </summary>
		/// <returns></returns>
		static double StandardDeviation<T>(IList<T> list, double mean, Func<T, double> func)
		{
			IList<double> listXi = new List<double>();
			foreach (var kv in list)
			{
				listXi.Add((func(kv) - mean) * (func(kv) - mean));
			}
			double sumXi = listXi.Sum();

			double d2 = sumXi / (list.Count - 1);
			double d = Math.Sqrt(d2);
			return d;
		}


		static IList<T> GetGood<T>(IList<T> list, double mean, Func<T, double> func)
		{
			double sd3 = StandardDeviation(list, mean, func) * 3;//3倍标准差
			IList<T> resList = new List<T>();
			foreach (var kv in list)
			{
				if (Math.Abs(func(kv) - mean) < sd3)
				{
					resList.Add(kv);
				}
			}
			return resList;
		}

		/// <summary>
		/// 拉依达剔除异常数据
		/// </summary>
		/// <param name="list">List<T>数组</param>
		/// <param name="sum">需要剔除字段的总值</param>
		/// <param name="func">需要剔除的字段</param>
		/// <returns></returns>
		public static IList<T> GetGoodList<T>(IList<T> list, double sum, Func<T, double> func)
		{
			//平均值
			var mean = SetMean(list, sum);
			bool isRun = true;
			IList<T> reslist = list;
			while (isRun)
			{
				int num = reslist.Count;
				reslist = GetGood(list, mean, func);
				if (reslist.Count == num)
				{
					isRun = false;
				}
			}
			return reslist;
		}
	}
}