MATLAB: Retime timetable out of bounds

retimetimetable

I have a set of timetables inside a cell TT, each of them with a resolution of 15 minutes, the timetables have different starts and ends, different sizes (missing data for each are different). What I want to do is set all these time tables to a common time vector, and then fill all the missing data with NaN. If I use retime (for one timetable) in this from:
TT1new = retime(TT{1},'regular','fillwithmissing','TimeStep',minutes(15));
it fills NaN but within the time range of TT1, and not of my time vector. So it seems to me that in order to use my time vector "retime" is of no use, instead I have done the following:
tini = datetime({'01-Apr-2016 00:00:00'});
tfin = datetime({'01-Apr-2017 00:00:00'});
timeVector = [tini:datenum([0,0,0,0,15,0]):tfin]';
%I built a reference timetable full of NaN, (I have 3 variables in each timetable)
ttref = timetable(timeVector,NaN(length(timeVector),1),NaN(length(timeVector),1),NaN(length(timeVector),1));
%Then I plan to fill the non-missing data in the reference timetable for each timetable, and capture the result in TTFit
num = length(TT);
TTFit = cell(num,1);
for i=1:num
        temp=ttref;
        range = timerange(max(tini,TT{i}.Time(1)),min(tfin,TT{i}.Time(end)),'closed');
        temp(TT{i}(range,:).Time,:).Variables = TT{i}(range,:).Variables;
        TTFit{i}=temp;
end
But it takes an eternity (more than 20 minutes so far and yet dont know if it works) to finish the run. Is there an easier and efficient way to do that? Any hints would be really apreciatted.

Best Answer

Hi Rub,
First, about your code examples I have some suggestions. I saw you used datenum in your first post. It is good that you replaced datenum with minutes in your second post. It's never a good idea to mix datenum with the newer and preferred datetime. About preallocating a timetable, you can also do it by using timetable preallocation syntax as the following. 
ttref = timetable('Size', [length(timeVector), 3], 'VariableTypes', ["double" "double" "double"], 'RowTimes', timeVector);
To answer your question, retime is the right tool for your job. Retime has a syntax TT2 = retime(TT1,NEWTIMES). You can use TTFit{i}=retime(TT{i},timeVector) in your for-loop. Your code will look like the following:
tini = datetime({'01-Apr-2016 00:15:00'});
tfin = datetime({'07-Apr-2017 00:00:00'});
timeVector = [tini:minutes(15):tfin]';
num = length(TT);
TTFit = cell(num,1);
for i=1:num
    TTFit{i}=retime(TT{i},timeVector);
end
Furthermore, you can use cellfun to replace your for-loop as
tini = datetime({'01-Apr-2016 00:15:00'});
tfin = datetime({'07-Apr-2017 00:00:00'});
timeVector = [tini:minutes(15):tfin]';
TTFit = cellfun(@(tt)retime(tt, timeVector),TT,'UniformOutput',false);
This runs faster.
I’m interested in why you put your timetables in a cell array, and what you will do with it next. If you are going to concatenate then all to make one timetable, then synchronize is the tool that can help you. Steve suggested calling synchronize using a comma-separated list, which you may not have seen before. Here's what that looks like:
TTFit = synchronize(TT{:},timeVector);
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