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How to I parse an array of time stamp strings read into a table form a CSV file?

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I have time stamped data collected into a csv file which I bring into Matlab as table.:
curr=
1053×2 table
Time Current
_________________________ ____________________________
"02/27/2024, 12:03:25 PM" -0.329
"02/27/2024, 12:03:30 PM" -0.14
"02/27/2024, 12:03:35 PM" -0.0765
"02/27/2024, 12:03:40 PM" -0.182
"02/27/2024, 12:03:45 PM" -0.292
I ultimately want to change the times into durations to plot the data vs. relative time; for example, the first entry would be time 0, the second would be 5 seconds later, etc...
I've tried something like this.:
time = split(curr.Time(:,1),'P')
time = split(time(:,1),',')
time = strip(time(:,2))
time = char(time(1:end-1))
time = duration(string(time(:,1:end-1)))
at this point I'm left with an array of duraitons. If I then subtract the first entry, I get the durations:
secs = time
secs = secs- secs(1)
However, because I got rid of the PM, I end up with negative seconds when the hour changed from 12 to 1. So, I tried and "if statement" to add 12 to any hour less than 12, but I couldn't do it.
if hour(string(time_curr_NHP))<12
hour(string(time_curr_NHP)) = hour(string(time_curr_NHP))+12
end
I'm pretty sure I've complicated this a lot more than it needs to be! There has to be a much simpler way to do this. I'd appreciate any help.
Thank you.

Accepted Answer

Les Beckham
Les Beckham on 1 Mar 2024
Edited: Les Beckham on 1 Mar 2024
Don't operate on the timestamps as strings, use the datetime and duration types and the associated functions.
times = linspace(datetime(2024, 3, 1, 11, 30, 0), datetime(2024, 3, 1, 12, 25, 0), 12)';
times.Format = 'MM/dd/uuuu hh:mm:ss a'
times = 12×1 datetime array
03/01/2024 11:30:00 AM 03/01/2024 11:35:00 AM 03/01/2024 11:40:00 AM 03/01/2024 11:45:00 AM 03/01/2024 11:50:00 AM 03/01/2024 11:55:00 AM 03/01/2024 12:00:00 PM 03/01/2024 12:05:00 PM 03/01/2024 12:10:00 PM 03/01/2024 12:15:00 PM 03/01/2024 12:20:00 PM 03/01/2024 12:25:00 PM
curr = table(times, rand(12, 1), 'VariableNames', {'Timestamp', 'Current'}) % Example table
curr = 12×2 table
Timestamp Current ______________________ ________ 03/01/2024 11:30:00 AM 0.90385 03/01/2024 11:35:00 AM 0.13638 03/01/2024 11:40:00 AM 0.99377 03/01/2024 11:45:00 AM 0.025041 03/01/2024 11:50:00 AM 0.11393 03/01/2024 11:55:00 AM 0.43305 03/01/2024 12:00:00 PM 0.77071 03/01/2024 12:05:00 PM 0.92144 03/01/2024 12:10:00 PM 0.28531 03/01/2024 12:15:00 PM 0.29388 03/01/2024 12:20:00 PM 0.78679 03/01/2024 12:25:00 PM 0.49889
secs = timeofday(curr.Timestamp)
secs = 12×1 duration array
11:30:00 11:35:00 11:40:00 11:45:00 11:50:00 11:55:00 12:00:00 12:05:00 12:10:00 12:15:00 12:20:00 12:25:00
secs = seconds(secs - secs(1))
secs = 12×1
0 300 600 900 1200 1500 1800 2100 2400 2700
class(secs)
ans = 'double'

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