Select specified (max) values
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Dear all, I've a matrix, e.g.:
A = [2 1 1 1440 62 2 6 8; 2 2 1 1882 65 2 7 8; 3 1 1 820 51 2 5 8; 3 2 1 1435 65 2 6 8; 3 3 1 1608 67 2 6 8; 9 1 1 394 38 1 2 8;9 2 1 2198 93 2 9 8; 9 2 2 2198 91 2 12 8; 9 2 3 2198 92 2 16 8; 9 3 1 2994 122 1 7 8; 9 3 2 2994 125 1 10 8; 9 3 3 2994 126 1 14 8];
For each row with the same value in the 1st and 2nd column, I've to take only the row where the 3th column is the maximum. I would, as result, a matrix like this:
B = [2 1 1 1440 62 2 6 8; 2 2 1 1882 65 2 7 8; 3 1 1 820 51 2 5 8; 3 2 1 1435 65 2 6 8; 3 3 1 1608 67 2 6 8; 9 1 1 394 38 1 2 8; 9 2 3 2198 92 2 16 8; 9 3 3 2994 126 1 14 8];
[key, ~, index] = unique(A(:,[1 2]),'stable','rows');
x = accumarray(index, A(:,3), [], @max);
...and I'm blocked here!
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Jan
2017년 2월 12일
편집: Jan
2017년 2월 12일
You can start with sorting the array according to the first 3 columns. Then take the rows which contain a change in the 1st or 2nd column, and the last row:
S = sortrows(A, 1:3); % Largest 3rd col to bottom
Index = [diff(S(:, 1)) | diff(S(:, 2)); true]; % 1st or 2nd col changes
B = A(Index, :) % Extract result
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