Duration in double between two datenum

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Luis Ruiz
Luis Ruiz 2018-9-7
评论： Peter Perkins 2018-9-12
I have two dates given in text format, I want to have the real duration in seconds between the two values.
The answer is -24, and I can do it parsing the strings. But does MATLAB have a function to do it nice and quick?
If I do the following the answer is not a -24 that I can use as a double:
datenum('2018-09-07 18:36:05.079')-datenum('2018-09-07 18:36:29.079')
I need this time for a Simulink simulation. For example, I might need the duration in seconds between two days.

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采纳的回答

Stephen23
Stephen23 2018-9-7
编辑：Stephen23 2018-9-7
To get seconds simply multiply the days by 60*60*24:
>> F = 'yyyy-mm-dd HH:MM:SS.FFF';
>> D = datenum('2018-09-07 18:36:05.079',F)-datenum('2018-09-07 18:36:29.079',F);
>> D*60*60*24
ans = -24.000
  2 个评论
Luis Ruiz
Luis Ruiz 2018-9-10
编辑：Luis Ruiz 2018-9-10
This one seems to be the right answer, but then, does it mean that operations between two datenum values are always in days?
Stephen23
Stephen23 2018-9-10
@Luis Ruiz: yes, datenum always returns days. But the conversion to seconds is trivial, as my answer shows.

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更多回答（2 个）

Peter Perkins
Peter Perkins 2018-9-7
If possible, don't use datenum. Use datetimes:
>> fmt = 'yyyy-MM-dd HH:mm:ss.SSS';
>> dur = datetime('2018-09-07 18:36:05.079','Format',fmt) - datetime('2018-09-07 18:36:29.079','Format',fmt)
dur =
duration
-00:00:24
>> dur.Format = 's'
dur =
duration
-24 sec
  3 个评论
显示 1更早的评论
Peter Perkins
Peter Perkins 2018-9-12
As James says, you can convert, but the point of duration is that you may not need a number. duration supports all kinds of time arithmetic. Hard to know if that's possible in your case.

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Image Analyst
Image Analyst 2018-9-7
编辑：Image Analyst 2018-9-10
Try the etime() function.
t1 = datevec('2018-09-08 18:36:05.079','yyyy-mm-dd HH:MM:SS.FFF')
t2 = datevec('2018-09-07 18:36:29.079','yyyy-mm-dd HH:MM:SS.FFF')
elapsedTime = etime(t1, t2) % Results in seconds.

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