C# 使用c LINQ计算分组字段的平均值

有人可以帮助我使用c Linq计算以下数据的平均值：

Year    city1   city2   value  
2016    CIT01   CIT01   578
2016    CIT01   CIT02   1067
2016    CIT01   CIT03   17
2016    CIT02   CIT01   1105
2016    CIT02   CIT02   233
2016    CIT02   CIT03   0
2016    CIT03   CIT01   1425
2016    CIT03   CIT02   231
2016    CIT03   CIT03   1398
2017    CIT01   CIT01   185
2017    CIT01   CIT02   69
2017    CIT01   CIT03   2225
2017    CIT02   CIT01   0
2017    CIT02   CIT02   104
2017    CIT02   CIT03   258
2017    CIT03   CIT01   10
2017    CIT03   CIT02   342
2017    CIT03   CIT03   643
2018    CIT01   CIT01   59
2018    CIT01   CIT02   163
2018    CIT01   CIT03   284
2018    CIT02   CIT01   19
2018    CIT02   CIT02   379
2018    CIT02   CIT03   462
2018    CIT03   CIT01   46
2018    CIT03   CIT02   0
2018    CIT03   CIT03   154

在示例中，我希望得到以下各项的平均值： 2016 CIT01 CIT01 578 2017 CIT01 CIT01 185 2018 CIT01 CIT01 59

输出：

Year   city1   city2   value
-----------------------------
Prev    CIT01   CIT01   274
Prev    CIT01   CIT02   433
Prev    CIT01   CIT03   842
Prev    CIT02   CIT01   375
Prev    CIT02   CIT02   239
Prev    CIT02   CIT03   240
Prev    CIT03   CIT01   494
Prev    CIT03   CIT02   191
Prev    CIT03   CIT03   732

---

一种方法是按city1和city2值分组，然后选择一个新项目，其中年份为上一年，城市与组中的城市相同，值为group.Averageg=>g.value。我们可以使用Math.Ceiling方法强制向上取整，就像您在示例中所做的那样

例如，给定以下类来保存数据：

public class Data
{
    public string Year { get; set; }
    public string City1 { get; set; }
    public string City2 { get; set; }
    public int Value { get; set; }

    public Data(string year, string city1, string city2, int value)
    {
        Year = year;
        City1 = city1;
        City2 = city2;
        Value = value;
    }

    public override string ToString()
    {
        return $"{Year} {City1} {City2} {Value}";
    }
}

以及以下列表来保存问题的初始值：

var allData = new List<Data>
{
    new Data("2016", "CIT01", "CIT01", 578),
    new Data("2016", "CIT01", "CIT02", 1067),
    new Data("2016", "CIT01", "CIT03", 17),
    new Data("2016", "CIT02", "CIT01", 1105),
    new Data("2016", "CIT02", "CIT02", 233),
    new Data("2016", "CIT02", "CIT03", 0),
    new Data("2016", "CIT03", "CIT01", 1425),
    new Data("2016", "CIT03", "CIT02", 231),
    new Data("2016", "CIT03", "CIT03", 1398),
    new Data("2017", "CIT01", "CIT01", 185),
    new Data("2017", "CIT01", "CIT02", 69),
    new Data("2017", "CIT01", "CIT03", 2225),
    new Data("2017", "CIT02", "CIT01", 0),
    new Data("2017", "CIT02", "CIT02", 104),
    new Data("2017", "CIT02", "CIT03", 258),
    new Data("2017", "CIT03", "CIT01", 10),
    new Data("2017", "CIT03", "CIT02", 342),
    new Data("2017", "CIT03", "CIT03", 643),
    new Data("2018", "CIT01", "CIT01", 59),
    new Data("2018", "CIT01", "CIT02", 163),
    new Data("2018", "CIT01", "CIT03", 284),
    new Data("2018", "CIT02", "CIT01", 19),
    new Data("2018", "CIT02", "CIT02", 379),
    new Data("2018", "CIT02", "CIT03", 462),
    new Data("2018", "CIT03", "CIT01", 46),
    new Data("2018", "CIT03", "CIT02", 0),
    new Data("2018", "CIT03", "CIT03", 154),
};

输出

---

可能重复的请在询问堆栈溢出之前进行一些搜索。@HereticMonkey此链接不会同时处理多个或嵌套的分组字段您的问题没有提到多个或嵌套的分组字段。它逐字询问如何计算分组字段的平均值，这就是建议的重复答案。请看。为什么在预期结果中，年值变为上一个值？

var results = allData
    .GroupBy(d => new {d.City1, d.City2})
    .Select(group => new Data("Prev", group.Key.City1, group.Key.City2,
        (int) Math.Ceiling(group.Average(g => g.Value))))
    .OrderBy(d => d.City1)
    .ThenBy(d => d.City2);

foreach (var result in results)
{
    Console.WriteLine(result);
}