使用Linq来统计数据的平均值

Question

我有一个名为HardwarePerformance的类包含这些字段：time，cpuUsagePercent，memoryUsagePercent，diskUsage，diskRead，diskWrite，latency。 我已经填充List对象来包含非统计数据。 我需要计算Linq命令中所有这些字段的平均值。 我不知道如何获得Linq的平均值。 Follow是我写的代码（当然是不正确的）。

var _hardwarePerf = (from _stats in _statsList 
        where _time>=DateTime.Parse("2012-04-04 00:00:00") 
         &&_time<=DateTime.Parse("2012-04-04 11:00:00") 
        select new { 
          Latency = _stats.latency, 
          CpuUsagePercent = _stats.cpuUsagePercent, 
          MemoryUsagePercent = _stats.memoryUsagePercent, 
          DiskUsage = _stats.diskUsage, DiskRead = _stats.diskRead, 
          DiskWrite = _stats.diskWrite 
        }).Average(Latency => Latency.Latency); 

该代码的语法是正确的。但我想同时计算所有的平均值，我该如何编写我的代码？

Answer 1

您可以使用“分组依据”，然后您可以使用平均投影来计算。

var query = from _stats in _statsList 
    group _stats by new { 
       Latency = _stats.latency, 
       CpuUsagePercent = _stats.cpuUsagePercent, 
       MemoryUsagePercent = _stats.memoryUsagePercent, 
       DiskUsage = _stats.diskUsage, 
       DiskRead = _stats.diskRead, 
       DiskWrite = _stats.diskWrite 

    } into myGroup 
    select new { 
     AverageVal = myGroup.Average(x => x.Value), 
     CpuUsagePercent = myGroup.Key.CpuUsagePercent, 
     ... // the rest of your projection 
}; 

LINQ Average

Answer 2

有一个在LINQ对此没有内置的方法。如果您不介意多次迭代集合，并假设匿名对象对您可以，则可以这样做（其中filteredStats包含要平均的数据，可能按时间过滤）：

var averages = 
    new 
    { 
     Latency = filteredStats.Average(x => x.Latency), 
     CpuUsagePercent = filteredStats.Average(x => x.CpuUsagePercent), 
     … 
    }; 

如果这不是你想要的，你可能需要自己计算平均值。

Answer 3

以下计算一次迭代中的所有平均值，虽然它有很多代码。

请注意，我假设time是您的统计资料对象的属性，否则您的select where time没有多大意义。

var _hardwareAccumulator = 
    _statsList 
     .Where(s => 
      s.time >= DateTime.Parse("2012-04-04 00:00:00") && 
      s.time <= DateTime.Parse("2012-04-04 11:00:00")) 
     .Aggregate(
      new 
      { 
       count = 0, 
       cpuUsagePercent = 0.0, 
       memoryUsagePercent = 0.0, 
       diskUsage = 0.0, 
       diskRead = 0.0 
      }, 
      (acc, s) => 
       new 
       { 
        count = acc.count + 1, 
        cpuUsagePercent = 
         acc.cpuUsagePercent + s.cpuUsagePercent, 
        memoryUsagePercent = 
         acc.memoryUsagePercent + s.memoryUsagePercent, 
        diskUsage = 
         acc.diskUsage + s.diskUsage, 
        diskRead = 
         acc.diskRead + s.diskRead 
       } 
      ); 
var _hardwarePerf = new 
{ 
    cpuUsagePercent = 
     _hardwareAccumulator.cpuUsagePercent/_hardwareAccumulator.count, 
    memoryUsagePercent = 
     _hardwareAccumulator.memoryUsagePercent/_hardwareAccumulator.count, 
    diskUsage = 
     _hardwareAccumulator.diskUsage/_hardwareAccumulator.count, 
    diskRead = 
     _hardwareAccumulator.diskRead/_hardwareAccumulator.count 
}; 

Answer 4

你要么东东做，在单独的语句或者你可以做到这一点在这不是很直观的方式：

var averages = statsList.Where(s => s.time >= new DateTime(2012, 4, 4) && s.time <= new DateTime(2012, 4, 04, 11, 0, 0)) 
      .GroupBy(s => 1) 
      .Select(grp => new 
      { 
       Latency = grp.Average(s => s.latency), 
       CpuUsagePercent = grp.Average(s => s.cpuUsagePercent), 
       MemoryUsagePercent = grp.Average(s => s.memoryUsagePercent), 
       DiskUsage = grp.Average(s => s.diskUsage), 
       DiskRead = grp.Average(s => s.diskRead), 
       DiskWrite = grp.Average(s => s.diskWrite) 
      }).FirstOrDefault(); 

注意.GroupBy(s => 1)只是为了能够计算平均每个属性。另请注意，我已从您的房产名称中删除下划线，并将时间添加到您的班级。

另一种方法更容易阅读：

var theStats = statsList.Where(s => s.time >= new DateTime(2012, 4, 4) && s.time <= new DateTime(2012, 4, 04, 11, 0, 0)); 
var Latency = theStats.Average(s => s.latency); 
var CpuUsagePercent = theStats.Average(s => s.cpuUsagePercent); 
// ....