Timedata 'dd-mmm-yyyy HH:MM:SS' transform into seconds

Hello,

I got a excel data in xlsx or csv, which looks like in the picture.

The time vector should be transformed into seconds, so i wrote this code.

Matlab throws me an error. How can i transform it into seconds?

Thank you for Help!

NTtemp=xlsread('Data.xlsx');     
out=datestr(NTtemp(StartZeitInZeile:end,1),'dd-mmm-yyyy HH:MM:SS');  
NTneueZeit=[datenum( out, 'dd-mmm-yyyy HH:MM:SS' ) .* (24*60*60) - datenum( out(1,:), 'dd-mmm-yyyy HH:MM:SS' ) .* (24*60*60)]; 
NT(:,1)=NTneueZeit;                                      
NT(:,2)=NTtemp(StartZeitInZeile:end,2); 

Answer 1

[Steven Lord]

I would avoid going through datenum and datestr. Instead I would import that column of data as a datetime array (which I believe readtable will do for you automatically.) If you then need the number of seconds since a particular time as an additional variable in that table, that's fairly straightforward. I'm going to compute how many seconds have elapsed since midnight.

rightnow = datetime('now')
lastMidnight = dateshift(rightnow, 'start', 'day')
elapsedSeconds = seconds(rightnow-lastMidnight)

As I type this it's about 10:30 in the morning, so elapsedSeconds should be about 37800 (10.5*3600). Your elapsedSeconds may be different depending on your time zone.

[Peter Perkins]

Better yet ...

elapsedTime = rightnow-lastMidnight

That leaves elapsedTime as a duration, and you no longer need to worry about units.