Thread Subject: subtracting time difference

hi

i have some data that i am recording the time that it enters
the serial port. it is currently been written to a file, but
i would also like to find the difference in time between the
sequences of data.

the data is stored in the file like this:

4f 09.22.569
63 09.22.588
67 09.22.613

with the first part being hex data and the second part is
the time stamp using datestr(now('MM.SS.FFF'));

how do i set it up so that it finds the difference in time
between 09.22.588 and 09.22.613? it cant be changed using
datenum because datenum doesnt recognise SS.FFF.

thanks in advance
jase

jason wrote:
> hi
>
> i have some data that i am recording the time that it enters
> the serial port. it is currently been written to a file, but
> i would also like to find the difference in time between the
> sequences of data.
>
> the data is stored in the file like this:
>
> 4f 09.22.569
> 63 09.22.588
> 67 09.22.613
>
> with the first part being hex data and the second part is
> the time stamp using datestr(now('MM.SS.FFF'));
>
> how do i set it up so that it finds the difference in time
> between 09.22.588 and 09.22.613? it cant be changed using
> datenum because datenum doesnt recognise SS.FFF.

Write your own function to handle the format you have.

All you need basically is 1000*(MM*60 + SS) + FFF for each numbers
(scaling to integers) for each number and then take the difference and
reverse the scaling.

Or, if not concerned about the minor amount of floating point roundoff
you could forget the scaling by 1000

timestampserial == MM*60 + SS.FFF

--

jason:
<SNIP may have an older ML version...

> datenum doesnt recognise SS.FFF.

well, here it does

<pre class="code">

% the data
     t1=datenum('09.12.111','MM.SS.FFF');
     t2=datenum('09.12.222','MM.SS.FFF');
     td=t2-t1
% the check
     datestr(t1,'MM.SS.FFF')
     datestr(td,'SS.FFF')

</pre>

us