Find rows in matrix based on columns value
显示 更早的评论
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 个评论
Andrei Bobrov
2019-9-2
find(mat(:,2) == 10 & mat(:,3) == 11)
采纳的回答
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
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
>>
更多回答（2 个）
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
Andrei Bobrov
2019-9-2
Hi Madhan!
Your result for follow case:
mat = [10 2 3 8
5 7 10 3
9 10 11 11];
>> row_index = find(sum(~mod(mod(mat,10),11),2)==1)
row_index =
1
2
3
>>
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)
Andrei Bobrov
2019-9-2
All right! +1.
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
Andrei Bobrov
2019-9-2
编辑：Andrei Bobrov
2019-9-2
for my case:
mat = [1 11 3 10
5 6 10 10
9 10 11 12];
Madhan's result:
>> ix = sum(ismember(mat,[10,11]),2)==2;
row_index = find(ix)
row_index =
1
2
3
>>
madhan ravi
2019-9-2
编辑：madhan ravi
2019-9-2
Ah thanks Andrei, +1
Robert U
2019-9-2
The description of the cited solution says "If you want to find the values 10 OR 11 within the matrix, and return the rows they have been found in, [...]". That is what it does.
Robert U
2019-9-2
What Steward Tan might want is to find rows containing 10 AND 11 within the matrix, but he did not describe it as that.
row = find(arrayfun(@(ind) any(mat(ind,:) == 10) & any(mat(ind,:) == 11),1:size(mat,1)));
Kind regards,
Robert
Andrei Bobrov
2019-9-2
I'm sorry Robert, my mistake!
Stewart Tan
2019-9-2
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