Find rows in matrix based on columns value

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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.

Accepted Answer

Robert U
Robert U on 2 Sep 2019
Edited: Robert U on 2 Sep 2019
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 Comments
madhan ravi
madhan ravi on 2 Sep 2019
? 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 on 2 Sep 2019
Edited: Robert U on 2 Sep 2019
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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More Answers (2)

madhan ravi
madhan ravi on 2 Sep 2019
Edited: madhan ravi on 2 Sep 2019
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 Comments
madhan ravi
madhan ravi on 2 Sep 2019
Edited: madhan ravi on 2 Sep 2019
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 on 2 Sep 2019
Edited: Andrei Bobrov on 2 Sep 2019
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 Comments
Stewart Tan
Stewart Tan on 2 Sep 2019
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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