Columns with at least one zero element

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Anya
Anya 2014-6-16
评论： dpb 2014-6-16
Hi,
If I have a matrix with random dimension mxn , how can I detect a column which have at least one zero element?
Thank you

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采纳的回答

Mischa Kim
Mischa Kim 2014-6-16
编辑：Mischa Kim 2014-6-16
Anya, you could use
A = [1 2 3 0 8; 5 0 1 2 2];
col = find(sum(A==0))
col =
2 4
col shows the columns which have at least one zero.
  1 个评论
dpb
dpb 2014-6-16
Just for comparison...
>> A = [1 2 3 0 8; 5 0 1 2 2];
>> (sum(A==0))
ans =
0 1 0 1 0
>> all(A)
ans =
1 0 1 0 1
>> ~all(A)
ans =
0 1 0 1 0
>>

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更多回答（2 个）

Jos (10584)
Jos (10584) 2014-6-16
Let M be your mxm matrix:
tf = any(M==0,1) % true for columns with at least 1 zero
C = M(:,~tf) % columns with no zeros
  2 个评论
Anya
Anya 2014-6-16
This answer also works ! thx guys
dpb
dpb 2014-6-16
NB:
any(M==0) --> identically equal to ~all(M). One rarely (if ever) needs to expressly test for zero.
See the doc for each for details...

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dpb
dpb 2014-6-16
idx=~all(M);

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