How do I get the value of seconds in a datetime table?

I collected some acceleration values using the matlab application, however i don't know how to convert the timestamps to seconds elapased.

[dpb]

'Pends. Are the timestamps real time or some other measure?

If real time, then just subtract the first value from the data.

[Hessa Lootah]

the timestamps from the sensor came out with the date(dd:mm:yy), time in hours, min, second and millisecond.

so basically subtract the first value from the last value and figure out how long that took?

Answer 1

[Cris LaPierre]

+1 to dpb's comment. Subtracting datetimes gives you a duration. You can convert your duration to your desired units - days, hours, minutes, seconds, etc by setting the duration format. See more here.

Some code taken from this example.

% Create a vetor of times
t = datetime('now') + minutes(1:0.25:3)

t = 1×9 datetime array
   03-Dec-2020 23:09:58   03-Dec-2020 23:10:13   03-Dec-2020 23:10:28   03-Dec-2020 23:10:43   03-Dec-2020 23:10:58   03-Dec-2020 23:11:13   03-Dec-2020 23:11:28   03-Dec-2020 23:11:43   03-Dec-2020 23:11:58

% compute elapsed time
dt = t - t(1)

dt = 1×9 duration array
   00:00:00   00:00:15   00:00:30   00:00:45   00:01:00   00:01:15   00:01:30   00:01:45   00:02:00

% convert elapsed time to seconds
dt.Format = 's'

dt = 1×9 duration array
     0 sec    15 sec    30 sec    45 sec    60 sec    75 sec    90 sec   105 sec   120 sec