Combine columns of a matrix based on equality

Question

Koren Murphy 2020-11-30

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https://ww2.mathworks.cn/matlabcentral/answers/669223-combine-columns-of-a-matrix-based-on-equality

评论： Ameer Hamza 2020-11-30

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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Answer 1

Ameer Hamza 2020-11-30

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https://ww2.mathworks.cn/matlabcentral/answers/669223-combine-columns-of-a-matrix-based-on-equality#answer_560318

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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

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Koren Murphy 2020-11-30

在 MATLAB Online 中打开

Also apoliges for the confusion it was my explanation that was at error here! The true example is:

a = [1 0 1 1; 1 0 1 0; 0 1 0 1];

so b should be

b = [2 0 1;2 0 0;0 1 1]

many thanks!

Ameer Hamza 2020-11-30

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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;