泛型列表的标准偏差？ [英] Standard deviation of generic list?

问题描述

我需要计算一个通用列表的标准偏差。我会尝试，包括我的code。它是一种通用的列表，在它的数据。这些数据主要是花车和整数。这里是我的code，是相对于它没有进入到很多细节：

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);
        }

<强>这里是标准偏差需要计算功能：

        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));

        }
    }
}

忽略什么的LatchStdev（）函数中，因为我敢肯定它不是正确的。它只是我可怜的尝试来计算ST开发。我知道怎么做了双打的名单中，但不是通用的数据列表的列表。如果有人在这过的经历，请大家帮忙。

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

本文应该可以帮助您。它创建一个计算双击值序列的偏差的功能。所有你需要做的就是提供合适的数据元素序列。

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.

由此产生的功能是：

private double CalculateStdDev(IEnumerable<double> values)
{   
  double ret = 0;
  if (values.Count() > 0) 
  {      
     //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      
     ret = Math.Sqrt((sum) / (values.Count()-1));   
  }   
  return ret;
}

这是很容易的为任何泛型类型相适应，只要我们提供所计算出的价值选择。 LINQ是伟大的是，选择功能可按允许您从普通的自定义类型的列表项目要计算标准差数值的序列：

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();

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