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.
1 commentaire
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Robert U
le 2 Sep 2019
Modifié(e) : Robert U
le 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 commentaires
madhan ravi
le 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
>>
Plus de réponses (2)
madhan ravi
le 2 Sep 2019
Modifié(e) : madhan ravi
le 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 commentaires
madhan ravi
le 2 Sep 2019
Modifié(e) : madhan ravi
le 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)
Andrei Bobrov
le 2 Sep 2019
Modifié(e) : Andrei Bobrov
le 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 commentaires
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