通用列表的标准偏差?

问题描述

我需要计算通用列表的标准偏差.我会尝试包含我的代码.它是一个包含数据的通用列表.数据主要是浮点数和整数.这是我的相关代码，没有详细介绍:

I need to calculate the standard deviation of a generic list. I will try to include my code. Its a generic list with data in it. The data is mostly floats and ints. Here is my code that is relative to it without getting into to much detail:

namespace ValveTesterInterface
{
    public class ValveDataResults
    {
        private List<ValveData> m_ValveResults;

        public ValveDataResults()
        {
            if (m_ValveResults == null)
            {
                m_ValveResults = new List<ValveData>();
            }
        }

        public void AddValveData(ValveData valve)
        {
            m_ValveResults.Add(valve);
        }

这里是需要计算标准差的函数:

        public float LatchStdev()
        {

            float sumOfSqrs = 0;
            float meanValue = 0;
            foreach (ValveData value in m_ValveResults)
            {
                meanValue += value.LatchTime;
            }
            meanValue = (meanValue / m_ValveResults.Count) * 0.02f;

            for (int i = 0; i <= m_ValveResults.Count; i++) 
            {   
                sumOfSqrs += Math.Pow((m_ValveResults - meanValue), 2);  
            }
            return Math.Sqrt(sumOfSqrs /(m_ValveResults.Count - 1));

        }
    }
}

忽略 LatchStdev() 函数内部的内容，因为我确定它不正确.这只是我计算 st dev 的拙劣尝试.我知道如何处理双打列表，但不知道如何处理通用数据列表.如果有人有这方面的经验，请帮忙.

Ignore whats inside the LatchStdev() function because I'm sure its not right. Its just my poor attempt to calculate the st dev. I know how to do it of a list of doubles, however not of a list of generic data list. If someone had experience in this, please help.

推荐答案

本文应该可以帮助你.它创建了一个函数来计算一系列 double 值的偏差.您所要做的就是提供一系列适当的数据元素.

This article should help you. It creates a function that computes the deviation of a sequence of double values. All you have to do is supply a sequence of appropriate data elements.

得到的函数是:

private double CalculateStandardDeviation(IEnumerable<double> values)
{   
  double standardDeviation = 0;

  if (values.Any()) 
  {      
     // Compute the average.     
     double avg = values.Average();

     // Perform the Sum of (value-avg)_2_2.      
     double sum = values.Sum(d => Math.Pow(d - avg, 2));

     // Put it all together.      
     standardDeviation = Math.Sqrt((sum) / (values.Count()-1));   
  }  

  return standardDeviation;
}

这很容易适应任何泛型类型，只要我们为正在计算的值提供一个选择器.LINQ 非常适合这一点，Select 函数允许您从自定义类型的通用列表中投影出一个数值序列，用于计算标准偏差:

This is easy enough to adapt for any generic type, so long as we provide a selector for the value being computed. LINQ is great for that, the Select funciton allows you to project from your generic list of custom types a sequence of numeric values for which to compute the standard deviation:

List<ValveData> list = ...
var result = list.Select( v => (double)v.SomeField )
                 .CalculateStdDev();