How select a first value from the binary matrix ?
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I have below matrix i want to select one value from each column which will be 1 make other 0 at return i will get 10*10 matrix.Selection of 1 such that a11 from 1st column,a22 from 2 column,a13 from the third column,a14 from the 4column and so on and make other value in the column 0.If we go for the indexing is ok for the small matrix but in bigger matrix we don't know the position of the 1 value.So is it possible to changed what i want.I have 1300*500 size matrix this is only for the example.
Thanks in advanced for your help.
matrix = [
0 1 0 0 1 0 0 1 0 1 0 1 1 1 0 1 0 0 1 0
1 1 0 0 1 1 1 0 0 1 0 1 0 1 0 0 1 1 1 1
0 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1
0 1 1 1 1 1 1 0 0 0 0 1 0 1 1 0 0 0 1 0
1 1 0 0 0 1 0 0 1 1 1 1 0 0 0 0 0 0 0 1
0 0 0 0 0 1 0 0 1 0 1 1 0 1 1 1 1 1 1 0
1 0 1 0 1 0 0 1 1 0 1 1 0 0 1 0 0 1 0 1
1 1 0 0 1 0 1 0 0 0 0 0 1 1 0 1 1 1 0 1
1 0 1 0 0 1 0 0 1 0 0 0 0 1 1 0 0 0 1 0
0 0 1 0 1 0 1 1 0 0 0 1 1 0 0 0 1 1 0 1
];
采纳的回答
Andrei Bobrov
2019-8-20
编辑：Andrei Bobrov
2019-8-22
out = cumsum(cumsum(matrix)) == 1;
or
out = cumsum(matrix) == 1 & matrix;
更多回答（1 个）
Walter Roberson
2019-8-19
编辑：Walter Roberson
2019-8-19
[~,idx] = max(matrix);
output = sparse(idx,1:size(matrix,2),1,size(matrix,1),size(matrix,2));
Note: in the case where there are no 1's in a particular column, then this code will pick the first row of that column.
[~,idx] = max(matrix);
output = sparse(idx,1:size(matrix,2),true,size(matrix,1),size(matrix,2));
is potentially more useful for your purposes.
5 个评论
vikash kumar
2019-8-19
编辑：vikash kumar
2019-8-19
Walter Roberson
2019-8-19
I am not sure what difference there is between what I provided and what you want. I suspect that you are being confused by the sparse() output. If so then
[~,idx] = max(matrix);
output = full(sparse(idx,1:size(matrix,2),true,size(matrix,1),size(matrix,2)));
vikash kumar
2019-8-20
darova
2019-8-20
You can also accept the answer. I will be pleased
Walter Roberson
2019-8-20
With your 1300 x 500 array, only 1 in 1300 rows has a non-zero entry for each column, so sparse can be a lot more storage efficient than full(); in my test, the full version takes 41 times more memory.
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