MATLAB: How to find the rows with the same values, and to merge those

concatenatefind the same valuematrix

I would want to know a way to find the rows having the same value in the first column (id), and combine those rows together.
Suppose I have the matrix A;
A = [1 2 3 4;
     1 5 6 0;
     2 2 3 4;
     2 5 6 0;
     2 6 7 8;
     3 1 2 3;
     4 1 2 3]
What I want to do is to find the rows with same ids (1st column), and merge their features (other columns). In this case, I need the following matrix.
A = [1 2 3 4 5 6 0 0;
     2 2 3 4 5 6 7 8;
     3 1 2 3 0 0 0 0;
     4 1 2 3 0 0 0 0];

Best Answer

Sounds like a homework assignment (tag it as homework if that's true), so how about I just get it started for you:
A = [1 2 3 4;
     1 5 6 0;
     2 2 3 4;
     2 5 6 0;
     2 6 7 8;
     3 1 2 3;
     4 1 2 3]
 % Find unique numbers in the first column.
 uniqueCol1 = unique(A(:,1))
 % Find out how many times each number occurs.
 counts = hist(A(:,1), uniqueCol1)
 % Find out how big our output matrix needs to be, and create it.
 rows = length(uniqueCol1);
 columns = 3 * max(counts);
 outputA = zeros(rows, columns, 'int32');
 % Assign first column
 outputA(:,1) = uniqueCol1
You can finish it.
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