MATLAB: Count the number of hours in a day (multiple values per hour)

arrayMATLABmatrixmatrix manipulationStatistics and Machine Learning Toolbox

Hello,
Please help me with the following.
Consider a matrix
M= [ 0 0 1 2 2 2 2 3 3 … 23 0 1 1 2 2 2 3 3 3 3 … 23 ];
These values corresponds to hours and my real matrix reaches up to 23.
I need to find per day how many values per hours existing. For example, the 1st day has two 0, one 1, three 2, two 3, etc, up to 23. The 2nd day has one 0, two 1, etc.
Thank you very much.
Best,
Pavlos

Best Answer

M = [0 0 1 2 2 2 2 3 3 23 0 1 1 2 2 2 3 3 3 3 23];
M = M(:); % columns are better
daybreaks = sign([diff(M); -5])==-1; % where do days split?
dayidx = repelem((1:sum(daybreaks)).',diff([0; find(daybreaks)]),1); % Which day
[mhour, ~, houridx] = unique(M); % unique hours
RecordsBYDay = accumarray([houridx, dayidx],1); % number of records for hour/day
table(mhour,RecordsBYDay)
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