How to find the multiple max values
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say like I have this 2D matrix
11 2 3 6
5 6 9 8
9 55 11 12
80 14 15 16
17 97 35 20
21 22 23 27
and I want to find the 4 largest values in column 3. How do I do that? *I did read some of the other posts but I can't seem to find anything conclusive.
采纳的回答
Walter Roberson
2017-2-22
dvals = sort(YourMatrix(:,3), 'descend');
largest4 = dvals(1:4);
8 个评论
Anonymous Matrix
2017-2-22
Walter Roberson
2017-2-22
[dvals, dindex] = sort(YourMatrix(:,3), 'descend');
largest4 = dvals(1:4);
index_of_largest4 = dindex(1:4);
jaah navi
2019-3-29
编辑：Walter Roberson
2019-5-29
With respect to the matrix
[11 2 3 6;
5 6 9 8;
9 55 11 12;
80 14 15 16;
17 97 35 20;
21 22 23 27]
how to frame the matrix such that it should display with two maximum values of each column and the other values to be zero.
lets say the output should be in the following manner
[0 0 0 0;
0 0 0 0;
0 55 0 0;
80 0 0 0;
0 97 35 0;
21 0 23 27]
Could you please help me on this.
Walter Roberson
2019-3-29
What should be done if there are duplicate matches? Three all the same, or one max and two copies of second best?
jaah navi
2019-5-29
with respect to the matrix
11 2 3 6
5 6 9 8
9 55 11 12
80 14 15 16
17 97 35 20
21 22 23 27
how to find the largest four values in all columns.
Guillaume
2019-5-29
Since this old answer has been revived, note that since R2017b you can use maxk which may or may not be faster than sorting the whole array/column. See also topkrows (R2016b or later) which may have been the ultimate goal here.
[largest4, indexoflargest4] = maxk(Yourmatrix(:, 3), 4);
%or
[largest4rows, indices] = topkrows(Yourmatrix, 4, 3);
@Jaah navi, as usual, when wanting to operate on the whole matrix reshape it into a single column with (:).
Walter Roberson
2019-5-29
What should be done if there are duplicate matches? Five all the same, or one max and four copies of second best, or one max and one second best and three copies of the third best, and so on? Your question contains no information about how you want to handle ties.
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