Wanting to analyze only data taken from days at night from a matrix of data from roughly a week

I have approximately a weeks worth of data (column 1 is date/time data in 30 second epochs and column two is the corresponding integer value for the date/time). I want to keep the entire data set (specifically date/time) for plotting purposes later on, but I only want to analyze the data in a function from 7pm to 10am on each day. Any recommendations on how to do this?

[Rik]

You should be able to use logical indexing.

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[Samantha Wallace]

I have attempted logical indexing and it hasn't been providing the end result I am looking for. Here, I have attached a sample of the data I am trying to analyze.

[Rik]

What code have you tried?

[Samantha Wallace]

I've tried many codes but in general the code below follows the format I've been trying most I think. It's pretty messy but I'm just stuck in a rut of how to make this work the way I am needing it to.

idx = strcmp(DT3_30str,{'19:00:15'});
[timeidx_7pm,~] = find(idx == 1);
idx = strcmp(DT3_30str,{'10:00:15'});
[timeidx_10am,~] = find(idx == 1);

for ii = 1:size(timeidx_7pm)
    if Sampledata(timeidx_7pm(ii):timeidx_10am(ii))
       Sampledata(ii,2) = Sampledata(ii,2);
    else
       Sampledata(ii,2) = {'DayTime'};  % or equal to rally anything as a place holder so I can still have the datetime value for plotting later
    end
end

Answer 1

[Steven Lord]

If your time and date data is stored as a datetime array, call hour on that datetime array.