Transformation from datetime to seconds

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Coginator
Coginator 2023-3-31
评论： Peter Perkins 2023-4-5
Hi,
I wanna do a transformation from datetime dd:MM:yyyy hh:mm:ss to seconds form a table.
this is my code (not the whole)
% Specify variable properties
opts = setvaropts(opts, "TimeAbs", "InputFormat", "dd.MM.yyyy HH:mm:ss");
% Import the data
tbl = readtable("Data.xlsx", opts);
%% Prepare data for calculations
TimeAbs = tbl.TimeAbs;
t = tbl.TimeRel; % [s]
I wanna make a vector TimeRel from the TimeAbs table
Thank you for your help

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回答（2 个）

Adam Danz
Adam Danz 2023-3-31
Ran in:
> I wanna do a transformation from datetime dd:MM:yyyy hh:mm:ss to seconds from a table
See a table of format identifies in the documentation
https://www.mathworks.com/help/matlab/ref/datetime.html#buhzxmk-1-Format
It's not clear whether you want to merely change the format to seconds or compute the difference and show that in seconds. I've shown both below.
TimeAbs = datetime(22,1,1,2,3,20,'Format','dd.MM.yyyy HH:mm:ss')+seconds(1:10)'
TimeAbs = 10×1 datetime array
01.01.0022 02:03:21 01.01.0022 02:03:22 01.01.0022 02:03:23 01.01.0022 02:03:24 01.01.0022 02:03:25 01.01.0022 02:03:26 01.01.0022 02:03:27 01.01.0022 02:03:28 01.01.0022 02:03:29 01.01.0022 02:03:30
TimeAbsSeconds = datetime(TimeAbs,'Format','ss.S')
TimeAbsSeconds = 10×1 datetime array
21.0 22.0 23.0 24.0 25.0 26.0 27.0 28.0 29.0 30.0
TimeAbsDiff = diff(TimeAbs)
TimeAbsDiff = 9×1 duration array
00:00:01 00:00:01 00:00:01 00:00:01 00:00:01 00:00:01 00:00:01 00:00:01 00:00:01
seconds(TimeAbsDiff)
ans = 9×1
1 1 1 1 1 1 1 1 1
  1 个评论
Peter Perkins
Peter Perkins 2023-4-5
Or even TimeAbs.Second to get the second component of the timestamps.
Cognator, to "transform to seconds", you have to say, "seconds from where?"

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Steven Lord
Steven Lord 2023-3-31
Ran in:
How do you want to perform this transformation? What does right now translate to in seconds?
N = datetime('now')
N = datetime
31-Mar-2023 13:46:55
Do you want to calculate the number of seconds since some fixed time that the datetime occurred?
midnight = datetime(2023, 3, 31) % or
midnight = datetime
31-Mar-2023
midnight = dateshift(N, 'start', 'day')
midnight = datetime
31-Mar-2023
We can create a duration that represents how long elapsed between midnight and now.
elapsed = N - midnight
elapsed = duration
13:46:55
If you need the number of seconds you can call seconds or (if you want to keep it a duration but change how it's presented) change the duration's Format property.
elapsedSeconds = seconds(elapsed) % or
elapsedSeconds = 4.9616e+04
elapsed.Format = 's' % Just change the format
elapsed = duration
49616 sec
As I type this elapsed is about 13 and 3/4 hours and elapsedSeconds is close to 50,000. Does that make sense?
estimate = 13.75*60*60 % 13.75 hours * 60 minutes/hour * 60 seconds/minute = units of seconds
estimate = 49500
That looks like reasonably close to the value I received in elapsed and elapsedSeconds.

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