对于异常值检测,我们可以使用一种称为"3倍中位数绝对偏差(3 times Median Absolute Deviation,3*MAD)"的方法。
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main(string[] args)
{
List<double> data = new List<double> { 0.1, 0.3, 0.27, 0.29, 18.7, 18.5, 0.3, 0.5, 0.9 };
List<double> outliers = FindOutliers(data);
Console.WriteLine("异常数据:");
foreach (double outlier in outliers)
{
Console.WriteLine(outlier);
}
}
public static List<double> FindOutliers(List<double> data)
{
List<double> outliers = new List<double>();
double median = CalculateMedian(data);
double mad = CalculateMAD(data, median);
foreach (double value in data)
{
if (Math.Abs(value - median) > 3 * mad) // 判断是否为异常值,这里使用3倍MAD作为判断条件
{
outliers.Add(value);
}
}
return outliers;
}
public static double CalculateMedian(List<double> data)
{
List<double> sortedData = data.OrderBy(x => x).ToList();
int n = sortedData.Count;
if (n % 2 == 0)
{
return (sortedData[(n / 2) - 1] + sortedData[n / 2]) / 2;
}
else
{
return sortedData[n / 2];
}
}
public static double CalculateMAD(List<double> data, double median)
{
List<double> absoluteDeviations = new List<double>();
foreach (double value in data)
{
absoluteDeviations.Add(Math.Abs(value - median));
}
double mad = CalculateMedian(absoluteDeviations);
return mad;
}
}