changing minutes after midnight into a datetime array

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AA
AA 2017-10-26
评论： Walter Roberson 2017-11-20
Suppose you have the matrix minutesaftermid which contains integers that represent the minutes after midnight, e.g. 1,2,3,4,5,6,7,......
How do I convert this format to a datetime array.
t = datetime(Y,M,D,H,MI,S,MS), but I only needs the MI.

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per isakson
per isakson 2017-10-26
编辑：per isakson 2017-10-26
"but I only need the MI" I don't think you can avoid the date and time.
X = 60*[1,2,3,4,5,6,7];
T = datetime( X, 'ConvertFrom','epochtime', 'Epoch','2000-01-01' )
T =
Columns 1 through 4
2000-01-01 00:01:00 2000-01-01 00:02:00 2000-01-01 00:03:00 2000-01-01 00:04:00
Columns 5 through 7
2000-01-01 00:05:00 2000-01-01 00:06:00 2000-01-01 00:07:00
and
>> T.Minute
ans =
1 2 3 4 5 6 7
Remark: the year 2000 is a leap year.

更多回答（2 个）

Walter Roberson
Walter Roberson 2017-10-26
datetime('today') + minutes(minutesaftermid)
if you wanted it to be relative to today (local time)
If you just need minutes after midnight and not any particular day, you should probably be leaving it as a duration array instead of a datetime array.
Peter Perkins
Peter Perkins 2017-11-16
datetimes are dates+times. As Walter says, unless you also have a set of dates, or you want 'today', then you likely want a duration array, and so just call the minutes function to create one.
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Peter Perkins
Peter Perkins 2017-11-20
Ah, right. So you can either add minutes (as you showed), or if you have the date portion as numeric values, you can use the "roll-over" behavior built into the constructor:
>> datetime(2017,11,1:3,0,[1430 1440 1450],0)
ans =
1×3 datetime array
01-Nov-2017 23:50:00 03-Nov-2017 00:00:00 04-Nov-2017 00:10:00
Walter Roberson
Walter Roberson 2017-11-20
I might...
T = datetime(2017,11,1:3,0,[1430 1440 1450],0, 'TimeZone', 'local');
[H, M] = hms(T);
mins_since_midnight = H * 60 + M
... though I would want to double-check outputs when there are time zone changes. I have now gotten myself confused about what "minutes since midnight" even means when there are time-zone changes.

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