Count top elements in a matrix (Matlab)

Question

I have the matrix:

A=[ 4 0 0 0 0
   0 3 0 0 0
   0 0 2 0 0
   0 0 0 1 0
   0 0 0 0 1 ];

I want to get the top k elements' values in the diag, such that the sum of these elements are larger than a predefined threshold T, whilst k is as large as possible.

For example: T= 0.9

            (4+3+2)/(trace(A)) = 0.818...
            (4+3+2+1)/(trace(A)) = 0.909...

i.e. we can get the vector of top values in A as: V= [4,3,2] and thus, k = 3.

Could anyone tell me how can I do that ?

how did you get the 10 from your D = 9/10 ? – GameOfThrows Mar 17 '16 at 09:57 — GameOfThrows, Mar 17 '16 at 09:57

Daniel · Accepted Answer · 2016-03-17T10:06:08.057

4

For the cumsum of diag(A) you want to find the last element where the comparison X./trace(A)<=T is true. Put that together into code:

find(cumsum(diag(A))./trace(A)<=T,1,'last')

edited Mar 17 '16 at 10:06

answered Mar 17 '16 at 09:59

Daniel

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I think you have the right result, I'm just going to delete my answer, I was really confused...I guess you could add a sort descend before the cumsum to make sure the ordering. – GameOfThrows Mar 17 '16 at 10:15

Count top elements in a matrix (Matlab)

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