# How to repeat number of array by values in another matrix

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Hamdia Mansour on 25 Jun 2020
Commented: Hamdia Mansour on 25 Jun 2020
Hello everybody I have an array like array=[3 4 2 1] and I want to create another array which contain repetition of values in this array by no of values in matrix. Matrix =[0 2 4 5; 1 3 2 6; 1 0 3 5; 5 6 3 1] Here for this array first no is 3 this mean repetition in matrix found in first column and row 3 which equal 1 and the second number is 4 also means that second column and forth row. so the resulted array will be 3 4 4 4 4 4 4 2 2 1 1 1 1 1 if someone could help me

Johannes Fischer on 25 Jun 2020
array = [3 4 2 1];
matrix = [0 2 4 5; 1 3 2 6; 1 0 3 5; 5 6 3 1];
% first, you need a vector with the same length of array that tells you
% how often each element must be repeated
reps = diag(matrix(array, :));
% now you can use 'repelem' with that vector
result = repelem(array, reps);

Stephen Cobeldick on 25 Jun 2020
+1 neat solution
Hamdia Mansour on 25 Jun 2020
Thank you very much Johannes fischer. You save my day. Thanks