Combine columns of a matrix based on equality
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I have a matrix of 1's and 0's and I would like to combine any column that repeats itself in the matrix - e.g if a is the matrix below I want b be the combination of any columns that are the same so b would be as shown - a new matrix with a combined repeated columns added togtehr and none repated ones left the same.
a = [1 1 1 0;1 0 0 0;0 0 0 1;1 1 1 0; 0 0 0 1]
b = [2 2 2 0; 1 0 0 0; 0 0 0 2];
The matrix I am actually dealing with is very large this is just a simplified version.
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Accepted Answer
Ameer Hamza
on 30 Nov 2020
Try this
a = [1 1 1 0;1 0 0 0;0 0 0 1;1 1 1 0; 0 0 0 1];
b = [2 2 2 0; 1 0 0 0; 0 0 0 2];
[M, ~, idx] = unique(a, 'rows', 'stable');
mul = histcounts(idx, 'BinMethod', 'integers').';
M = M.*mul;
Result
>> M
M =
2 2 2 0
1 0 0 0
0 0 0 2
3 Comments
Ameer Hamza
on 30 Nov 2020
The logic is same. Just a little modification is needed
a = [1 0 1 1; 1 0 1 0; 0 1 0 1];
b = [2 0 1;2 0 0;0 1 1];
[M, ~, idx] = unique(a.', 'rows', 'stable');
mul = histcounts(idx, 'BinMethod', 'integers');
M = M.'.*mul;
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