Find rows in matrix based on columns value

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Stewart Tan
Stewart Tan 2019-9-2
评论： Andrei Bobrov 2019-9-2
If i have a matrix:
mat = [1 2 3 4;
5 6 7 8;
9 10 11 12];
How do i find the row index where the column has value 10 and 11 for example? In this case, the row index will be 3 since it has columns with 10 and 11.
I tried doing something like:
find(mat(:,2) == 10 && mat(:,3) == 11)
But it doesn't work.

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采纳的回答

Robert U
Robert U 2019-9-2
编辑：Robert U 2019-9-2
Hi Steward Tan,
in the given matrix there is no single column that contains the values 10 AND 11. If you want to find the rows that contain 10 AND 11 you could use:
tmp = arrayfun(@(dIn) find(any(mat(dIn,:) == 10) & any(mat(dIn,:) == 11)),1:size(mat,1),'UniformOutput',false);
tmp(cellfun(@isempty,tmp)) = {0};
row = find(cell2mat(tmp));
If you want to find the values 10 OR 11 within the matrix, and return the rows they have been found in, one way might be:
mat = [1 2 3 4;
5 6 7 8;
9 10 11 12];
[row,~] = find(mat == 10 | mat == 11);
row = unique(row);
Kind regards,
Robert
  2 个评论
madhan ravi
madhan ravi 2019-9-2
? There are only three rows whereas this answer gives 6 & 9 ?
>> mat = [1 2 3 4;
5 6 7 8;
9 10 11 12];
[row,~] = unique(find(mat == 10 | mat == 11))
row =
6
9
>>
Robert U
Robert U 2019-9-2
编辑：Robert U 2019-9-2
My bad, the unique command needs to be written in an extra line to capture rows from find. I edited my answer.

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更多回答（2 个）

madhan ravi
madhan ravi 2019-9-2
编辑：madhan ravi 2019-9-2
ix = sum(ismember(mat,[10,11]),2)==2;
row_index = find(ix)
edit:
row_index = find(sum(~mod(mod(mat,10),11),2)==1)
  3 个评论
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madhan ravi
madhan ravi 2019-9-2
编辑：madhan ravi 2019-9-2
Yes Andrei, I realised just before your comment :). Hi Andrei, how about:
m=any(~mod(mat,10),2) & any(~mod(mat,11),2);
w=find(m)

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Andrei Bobrov
Andrei Bobrov 2019-9-2
编辑：Andrei Bobrov 2019-9-2
My case for mat:
mat = [1 11 3 10
5 6 10 10
9 10 11 12];
mat2 = sort(mat,2);
[m,n] = size(mat);
mat3 = mat2([(1:end-m)',(m+1:end)']);
iii = mod((1:m*n-m)'-1,m)+1;
out = sort(iii(ismember(mat3,[10,11],'rows')));
or
[i1,~] = find(mat == 10);
[i2,~] = find(mat == 11);
out = intersect(i1,i2);
another variant:
out = all(any(mat == reshape([10,11],1,1,[]),2),3);
  6 个评论
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Stewart Tan
Stewart Tan 2019-9-2
Thank you all for the various answers for this question of mine. Wish there was a way to accept more than one answers as they had been of good help. Voted up! Cheers!

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