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How do I gain indices of max values in 2D matrix?

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Klara
Klara 2014-4-8
回答： Jos (10584) 2014-4-10
For a 16 x 12 matrix I should sort it in descending order to gain the max values (like 10 in total). After that, I should find what was the indices of those max values before sorting .
I tried several times with sort and find. But it doesn't give me correct result.
  2 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2014-4-8
编辑：Azzi Abdelmalek 2014-4-8
You have two columns, you have to precise how you want to sort them
Azzi Abdelmalek
Azzi Abdelmalek 2014-4-8
You have a 16x12 matrix, there are several ways to sort your matrix, by rows or by columns? you have to give more details, or just show the result for a short example, if
A=[1 2;3 4;0 1;4 5 ;100 20;2 2;0 7]
What should be the result?

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回答（3 个）

Walter Roberson
Walter Roberson 2014-4-8
[sorted, idx] = sort(YourMatrix, 'rows', 'descend');
tenmax = idx(1:10);
  2 个评论
Klara
Klara 2014-4-8
Thanks but it gives me the indices of the max values, AFTER sorting!
Walter Roberson
Walter Roberson 2014-4-8
[sorted, idx] = sortrows(YourMatrix, -(1:size(YourMatrix,2)));
tenmax = idx(1:10);
this will give you the indices of the original rows that got sorted to the corresponding row position.

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Gautam
Gautam 2014-4-10
The answer above gives you the indices of before sorting. Try this example.
A = [1 4; 6 2; 4 2; 7 3]
[sortedMat,sortedIndex] = sort(A,'descend')
The sortedIndex matrix gives indices of the original rows (Note here that each column is sorted independently)
Jos (10584)
Jos (10584) 2014-4-10
Why sort first?
A = [1 4; 6 2; 4 2; 7 3]
[maxValues, RowIndex] = max(A,[],1)
LinearIndex = sub2ind(size(A),RowIndex, 1:size(A,2))
sortedA = sort(A,1,'descend')

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