MATLAB: Access data within timerange

endtimeMATLABstarttimetimerangetimetable

Hey guys,

I use timerange for accessing data in huge timetables (measurements) which works perfectly. I store these timeranges in cells.

However, in some cases it would be useful to get the starttime or endtime of a certain timerange, so another function can handle it (e. g. as a datetime). Or just to calculate the duration of the timerange.

I did not find anything like this, so I hope someone can help me! Thanks!

Best Answer

The timerange object is another of those opaque thingies TMW has fallen in love with that has useful stuff inside it that is hidden and not documented. :(

You can get the two interval values and the type of interval as two-step process--

s=timerange(t1,t2);
ss=struct(s);           % convert the timerange object to a struct that reveals internals
t1=ss.first;            % retrieve the start
t2=ss.last;             % end times in timerange s

However, since you have to have set t1,t2 for the timeranage object when you created it; it would be more straightforward to create your own "object" or array of objects that contains the information for the specific tmerange then. At the convenience of not having to carry those around but being able to reconstruct on demand for any specific timerange at hand.

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MATLAB: Comparing datetime value from two tables

A datetime always has an hour, minute, second component. The display format of the datetime array may be such that it is not shown, but it is always there. If you've read that array from a text file which didn't have a time component, then it defaults to 00:00:00.

You have several options to compare datetime arrays using just the date

You could set the time component in a to 00:00:00 and use standard comparison functions (e.g. ismember, or join)
You could extract the year, month and day from each with ymd and do array comparison (e.g. with ismember with the 'rows' option)
You could extract the date as strings (using char or datestr) and compare the strings.

Going with option 2, you could do:

ymda = zeros(height(a), 3);
[ymda(:, 1), ymda(:, 2), ymda(:, 3)] = ymd(a.Datetime);
ymdb = zeros(height(b), 3);
[ymdb(:, 1), ymdb(:, 2), ymdb(:, 3)] = ymd(b.Date);
queryresult = b(ismember(ymdb, ymda, 'rows'), :);  %equivalent to select * from b where b.date = a.date

MATLAB: Timerange in a loop

Yes. Build datetime objects using the three-input syntax and use them to construct a timerange. I left off one of the semicolons in the example below so you can see that at each iteration a different timerange was built with a different year.

for theyear = 2012:2016
    beginDate = datetime(theyear, 01, 01);
    endDate = datetime(theyear, 02, 01);
    TR = timerange(beginDate, endDate)
    % Do something with TR
end

Best Answer

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