LINQ骨料和组按时间段 [英] LINQ aggregate and group by periods of time

问题描述

我想了解LINQ如何使用通过的时间间隔组数据;然后最好汇总各组。

I'm trying to understand how LINQ can be used to group data by intervals of time; and then ideally aggregate each group.

寻找具有明确的日期范围的例子不胜枚举，我被时期，如5分钟，1小时，1设法组。日

Finding numerous examples with explicit date ranges, I'm trying to group by periods such as 5-minutes, 1-hour, 1-day.

例如，我有一个包装一个DateTime与值的类：

For example, I have a class that wraps a DateTime with a value:

public class Sample
{
     public DateTime timestamp;
     public double value;
}

这些意见都包含在一个列表集合了一系列的：

These observations are contained as a series in a List collection:

List<Sample> series;

所以，通过时间和平均聚合值每小时时段组，我试图做是这样的：在

So, to group by hourly periods of time and aggregate value by average, I'm trying to do something like:

var grouped = from s in series
              group s by new TimeSpan(1, 0, 0) into g
              select new { timestamp = g.Key, value = g.Average(s => s.value };

这是根本性的缺陷，因为这组的时间跨度本身。我不知道如何使用的时间跨度（或代表一个区间的任何数据类型）查询。

This is fundamentally flawed, as it groups the TimeSpan itself. I can't understand how to use the TimeSpan (or any data type representing an interval) in the query.

推荐答案

您可以圆时间戳到下一个边界（即下降到过去最接近5分钟边界），并使用它作为您的分组：

You could round the time stamp to the next boundary (i.e. down to the closest 5 minute boundary in the past) and use that as your grouping:

var groups = series.GroupBy(x =>
{
    var stamp = x.timestamp;
    stamp = stamp.AddMinutes(-(stamp.Minute % 5));
    stamp = stamp.AddMilliseconds(-stamp.Millisecond - 1000 * stamp.Second);
    return stamp;
})
.Select(g => new { TimeStamp = g.Key, Value = g.Average(s => s.value) })
.ToList();

上面实现，通过在分组，这台分钟到前5中使用一个修改的时间戳分钟边界并删除秒和毫秒。当然的同样的方法可以用于其他时间段，即时间和天

Above achieves that by using a modified time stamp in the grouping, which sets the minutes to the previous 5 minute boundary and removes the seconds and milliseconds. The same approach of course can be used for other time periods, i.e. hours and days.

修改

在此基础上提出了样本输入：

Based on this made up sample input:

var series = new List<Sample>();
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(3) });
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(4) });
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(5) });
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(6) });
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(7) });
series.Add(new Sample() { timestamp = DateTime.Now.AddMinutes(15) });

制作了3组对我来说，其中一个分组时间戳3:05，一个有3:10和一个用下午3:20（您的结果可能会有所不同基于当前时间）。

3 groups were produced for me, one with grouping timestamp 3:05, one with 3:10 and one with 3:20 pm (your results may vary based on current time).

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