使用 Linq Skip and Take 计算 List<> 子集

Question

根据这个堆栈问题：How to calculate the rolling average of a C# array list?

您可以像这样在普通列表中取值的运行平均值：

List<int> numlist = new List<int>();
List<double> averages = Enumerable.Range(0, numlist.Count - 3).
                          Select(i => numlist.Skip(i).Take(4).Average()).
                          ToList();

我的问题：我希望能够在类列表的特定子集上做到这一点：

public class Data_Raw
{
    public DateTime DateDataRaw { set; get; }
    public double PriceRaw { set; get; }
    public double PercentageReturnsRaw { set; get; }

    public Data_Raw(DateTime _dateDataRaw,double _priceRaw, double _percentageReturnsRaw)
    {
        DateDataRaw = _dateDataRaw;                     //1
        PriceRaw = _priceRaw;
        PercentageReturnsRaw = _percentageReturnsRaw;
    }
}

List<Data_Raw> myRawData = new List<Data_Raw>();

我想在 myRawData 的类列表中计算 PriceRaw 数据的平均值。

编辑：

如果这是PriceRaw的数据：

myRawData[0].PriceRaw=2
myRawData[1].PriceRaw=3
myRawData[2].PriceRaw=4
myRawData[3].PriceRaw=5

如何得到PriceRaw后三个值的平均值，即= (3+4+5)/3 = 4。仅在myRawData.Skip之后直接可用

如果我尝试将其附加到myRawData[].PriceRaw.Skip，则跳过不可用

这个堆栈问题让我更接近，但无法弄清楚：Linq query a List of objects containing a list of object

Answer 1

我认为如果你使用理解语法，你会更容易管理它。即：

void Main()
{
    List<Data_Raw> myRawData = new List<Data_Raw> {
       new Data_Raw(new DateTime(2018,1,1), 2, 1),
       new Data_Raw(new DateTime(2018,1,2), 3, 1),
       new Data_Raw(new DateTime(2018,1,3), 4, 1),
       new Data_Raw(new DateTime(2018,1,4), 5, 1),
       new Data_Raw(new DateTime(2018,1,5), 6, 1),
       new Data_Raw(new DateTime(2018,1,6), 7, 1),
       new Data_Raw(new DateTime(2018,1,7), 8, 1),
    };

    var groupSize = 3;
    var result = from i in Enumerable.Range(0, myRawData.Count() - (groupSize - 1))
                 let myGroup = myRawData.Skip(i).Take(groupSize)
                 select new
                 {
                     Values = string.Join(",", myGroup.Select(rd => rd.PriceRaw.ToString())),
                     Average = myGroup.Average(rd => rd.PriceRaw)
                 };
}

public class Data_Raw
{
    public DateTime DateDataRaw { set; get; }
    public double PriceRaw { set; get; }
    public double PercentageReturnsRaw { set; get; }

    public Data_Raw(DateTime _dateDataRaw, double _priceRaw, double _percentageReturnsRaw)
    {
        DateDataRaw = _dateDataRaw;                     //1
        PriceRaw = _priceRaw;
        PercentageReturnsRaw = _percentageReturnsRaw;
    }
}

Answer 2

只需在numList 中选择您需要的值（见第一行）：

var numList = myRawData.Select(x => x.PriceRaw).ToList();
List<double> averages = Enumerable.Range(0, numlist.Count - 3).
                      Select(i => numlist.Skip(i).Take(4).Average()).
                      ToList();

另一种方法可能是：

List<double> averages = Enumerable.Range(0, myRawData.Count - 3).
                      Select(i => myRawData.Skip(i).Take(4).Select(x => x.PriceRaw).Average()).
                      ToList();