Get all row indices where values of to columns reach their maximum

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Georg Bauer
Georg Bauer 2023-2-3
评论： Les Beckham 2023-2-5
Hey,
i would like to get an array containing the indices of all rows in which the values of column 2 and 3 reach their maximum at the same time.
Example:
A = [1 2 3;
1 4 3;
2 4 3;
1 4 2];
Output should be an array containing the values 2 and 3 corresponding to row 2 and 3 of array A since the values in column 2 and 3 both reach their maximum at the same time.
Output = [2 3];
Thank You :-)

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Les Beckham
Les Beckham 2023-2-3
Ran in:
A = [1 2 3;
1 4 3;
2 4 3;
1 4 2];
m = max(A(:,2:end), [], 1)
m = 1×2
4 3
Output = find(all(ismember(A(:,2:end), m), 2))
Output = 2×1
2 3
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Voss
Voss 2023-2-4
Ran in:
@Georg Bauer: What should Output be when A is as follows?
A = [1 2 3;
1 4 3;
2 3 3;
1 4 2];
% get column-wise maxima:
m = max(A(:,2:end), [], 1);
The given answer will give [2; 3] since rows 2 and 3 both have all values in their 2nd and 3rd columns as elements of the column-wise maxima m ([3 4]):
Output = find(all(ismember(A(:,2:end), m), 2))
Output = 2×1
2 3
But I think you want the result to be row 2 only, since that's the only row where the column-wise maxima occur in the same row, in which case you can use this logic, to compare elements in each column individually:
Output = find(all(A(:,2:end) == repmat(m,size(A,1),1), 2))
Output = 2

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