C# linq 根据以前的数据创建与函数相关的新项-解网

问：

List<History> data = new List<History>(){   
 new History() {Symbol="a", Close = 1.0m, Date = new DateTime(2016, 2, 1) },
 new History() {Symbol="a", Close = 1.2m, Date = new DateTime(2016, 2, 2) },
 new History() {Symbol="a", Close = 1.3m, Date = new DateTime(2016, 2, 3) },
 new History() {Symbol="b", Close = 1.2m, Date = new DateTime(2016, 2, 1) },
 new History() {Symbol="b", Close = 1.2m, Date = new DateTime(2016, 2, 2) },
 new History() {Symbol="b", Close = 1.3m, Date = new DateTime(2016, 2, 3) },
};

var StockGroupList = data
 .GroupBy(o => o.Symbol)
 .OrderBy(o => o.Key)
 .ToList();

我想创建一个新的列表，例如

select new { Symbol, Close, Date, Vol};

这是两天的标准差，例如 at 是 for 和的函数。此外，第一天（例如）的默认值为。VolVolSymbol="a"2016, 2, 3close2016, 2, 32016, 2, 2Vol2016, 2, 1Vol = 0

预期输出：

List<dynamic> NewData = new List<dynamic>
{ 
 new { Symbol = "a", Close = 1.0m, Date = new DateTime(2016, 2, 1), Vol = 0 },
 new { Symbol = "a", Close = 1.0m, Date = new DateTime(2016, 2, 2), Vol = SD(Close of 2016, 2, 1, Close of 2016, 2, 2) },
 new { Symbol = "a", Close = 1.0m, Date = new DateTime(2016, 2, 3), Vol = SD(Close of 2016, 2, 2, Close of 2016, 2, 3) },
                                            ......
};

你可以简单地说，你可以看作是一个给定的函数。此外，如果参数是说，那我该怎么办？SD(x,y)SD(x,y) = x+ySDListList[Close of 2016, 2, 2, Close of 2016, 2, 3)]

如果是以下形式SD

decimal OneStdDev = (decimal)(new DescriptiveStatistics(data.Select(o => (double)o.Close)).StandardDeviation);

我该怎么办？

C# LINQ

var results = data          
                .Take(1)
                .Select(x=>new {x.Symbol, x.Close, x.Date, Vol = 0.0m})
                .Concat(data.Zip(data.Skip(1), (first,second) => 
                                 new 
                                 {
                                     second.Symbol, 
                                     second.Close, 
                                     second.Date, 
                                     Vol = first.Close + second.Close  // Use whatever logic you want.
                                 }
                        ));

输出：

Symbol =a, Close=1.0, Date=2/1/2016 12:00:00 AM, Vol = 0.0
Symbol =a, Close=1.2, Date=2/2/2016 12:00:00 AM, Vol = 2.2
Symbol =a, Close=1.3, Date=2/3/2016 12:00:00 AM, Vol = 2.5
Symbol =b, Close=1.2, Date=2/1/2016 12:00:00 AM, Vol = 2.5
Symbol =b, Close=1.2, Date=2/2/2016 12:00:00 AM, Vol = 2.4
Symbol =b, Close=1.3, Date=2/3/2016 12:00:00 AM, Vol = 2.5

查看此演示

C# linq 根据以前的数据创建与函数相关的新项

C# linq Create a new item related to a function against previous data

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