MATLAB: Sum of first column based on second column and storing results in a matrix

data analysisMATLAB

I have two columns in a matrix.
1st Column : duration
2nd column : Reference Number
I want to add all durations rows for each reference number and store it in a matrix where there is a single duration(sum) along with its unique reference number.
My table looks like below. For example I need a unique summed value of duration for each 3130 reference number. I tried to do it individually using below code but very time consuming. Can anyone please help me to loop it and store result in a matrix? Any guidance on this will be appreciated. Thanks.
idx = A(:,2)==3130;
s = sum(A(idx,1));
matlab.PNG

Best Answer

% Create fake data for the demo
A = [rand(30,1),randi(3,30,1)+1000]; 
% Calculate group sum and store in table
[groupID, groups] = findgroups(A(:,2));
groupsum = splitapply(@sum,A(:,1),groupID); 
T = table(groups,groupsum)
Result (will vary due to random draw).
T =
  3×2 table
    groups    groupsum
    ______    ________
     1001       2.122 
     1002      6.1048 
     1003      6.8219
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