Function to calculate seconds between times in hh:mm:ss string format

I want to create a function that takes two strings as inputs, tref and t, and computes and returns the number of seconds until t since tref. Both tref and t are strings in the format hh:mm:ss.

For example

function_name('20:00:00','22:53:44') 

should return

10424

And for simplicity, I want to require that hour, minute, and second values in t are greater than or equal to hour, minute, and second values in tref, respectively. Is there any way to do this without any built in matlab time/date functions?

Answer 1

[Tommy]

What if you can get by without your requirement for simplicity?

function ts = timediff(tref, t)
    tref = dot([3600 60 1], str2double(regexp(tref, ':', 'split')));
    t = dot([3600 60 1], str2double(regexp(t, ':', 'split')));
    if t > tref
        ts = t - tref;
    else
        error('t must be later than tref')
    end
end

>> timediff('20:00:00','22:53:44')

ans =

       10424

>> timediff('23:00:00','22:53:44')
Error using timediff (line 7)
t must be later than tref

You'll have to check the inputs more carefully and deal with any innappropriate values. e.g.

>> timediff('23:00','22:53:44')
Error using dot
A and B must be same size.

Error in timediff (line 2)
    tref = dot([3600 60 1], str2double(regexp(tref, ':', 'split')));

[Mark Nakers]

This is exactly what I needed, thank you so much for your help!

[Stephen23]

Using sscanf is simpler and much more efficient than regexp and str2double:

>> [3600,60,1]*sscanf('22:53:44','%f:') - [3600,60,1]*sscanf('20:00:00','%f:')
ans =
       10424

[Tommy]

Nice, thank you for the tip!