Find average of collection of TimeSpans

Question

I have collection of TimeSpans, they represent time spent doing a task. Now I would like to find the average time spent on that task. It should be easy but for some reason I'm not getting the correct average.

Here's my code:

private TimeSpan? GetTimeSpanAverage(List<TimeSpan> sourceList)
{
    TimeSpan total = default(TimeSpan);

    var sortedDates = sourceList.OrderBy(x => x);

    foreach (var dateTime in sortedDates)
    {
        total += dateTime;
    }
    return TimeSpan.FromMilliseconds(total.TotalMilliseconds/sortedDates.Count());
}

Please provide sample data and what result you are getting and what result you are expecting. BTW: The ordering is not necessary. — Daniel Hilgarth, Jan 13 '12 at 08:22

vc 74 · Accepted Answer · 2020-09-17T11:01:14.197

109

You can use the Average overload that takes a collection of long in parameter:

double doubleAverageTicks = sourceList.Average(timeSpan => timeSpan.Ticks);
long longAverageTicks = Convert.ToInt64(doubleAverageTicks);

return new TimeSpan(longAverageTicks);

edited Sep 17 '20 at 11:01

answered Jan 13 '12 at 08:23

vc 74

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This gives me a error: cannot convert from 'double' to 'long' – hs2d Jan 13 '12 at 08:43
1

Instead of Ticks you can also use `TotalSeconds` and then use `TimeSpan.FromSeconds` – V4Vendetta Jan 13 '12 at 08:50
@V4Vendetta Yes you can but you'll loose the sub second components which can be useful if your are timing short actions – vc 74 Jan 13 '12 at 08:51
@vc74 Well in that case you can have TotalMilliseconds, also in your case you are casting double to long so the loss is happening in this case too :) – V4Vendetta Jan 13 '12 at 08:54
@V4Vendetta Yes but only once the average has been calculated which is better than for every timespan. – vc 74 Jan 13 '12 at 08:55

score 12 · Answer 2 · answered Jan 13 '12 at 08:23

12

var average = new TimeSpan(sourceList.Select(ts => ts.Ticks).Average());

Note, your method returns a Nullable, but doesn't need to, unless you want to return null if the source list is empty, in which case just do a separate check first.

answered Jan 13 '12 at 08:23

George Duckett

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There is no `Enumerable.Average()` overload that returns `long` value, as well as there is no TimeSpan constructor that accept double as the argument, so the example is not building for me. To make it compile I was forced to add an explicit cast `(long)` of the argument: `var average = new TimeSpan((long)sourceList.Select(ts => ts.Ticks).Average());` – Konard Aug 20 '19 at 15:51

score 4 · Answer 3 · edited Jan 05 '18 at 09:35

4

In Addition to the above answer, I would suggest you take an average on the Seconds or MilliSeconds level (depending on what you require)

sourceList.Average(timeSpan => timeSpan.ToTalMilliseconds)

Now using this value you could arrive at the new TimeSpan using

TimeSpan avg = TimeSpan.FromMilliseconds(double value here)

edited Jan 05 '18 at 09:35

wonea

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answered Jan 13 '12 at 08:57

V4Vendetta

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I just want to warn everyone that if your average is not even one millisecond, than because of [some precision problems](http://stackoverflow.com/a/5450832/1108200) your new average `TimeSpan` will be always 0. – Artholl Oct 29 '15 at 12:44
@Artholl That was my exact problem – Paul C Nov 17 '16 at 21:35

Find average of collection of TimeSpans

3 Answers3

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