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

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.

Answer 1

[Les Beckham]

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'

[Jorge]

I appreciate the detailed answer demonstrating how to use the datetime and duration types and the associated functions. Thanks!

[Les Beckham]

You are quite welcome.