Ranking row values of matrix without adjustment

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Tommaso Fornaciari
Tommaso Fornaciari 2016-12-4
评论： Jos (10584) 2016-12-5
Hello, I have a matrix that is 8000x600 and I need an output matrix of the same dimensions, containing the ranks of each element per row. I have used tiedrank but this averages the two ranks of equal observations and assigns to both that rank, which is not useful for me.
To make it simple, if I have [ 7 6 2 9 2] I would like the output to have [4 3 1 5 2] so that the value "2" gets 2 different ranks and not the average as [4 3 1.5 5 1.5].
Thank you in advance for your help

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回答（1 个）

Jos (10584)
Jos (10584) 2016-12-4
for a vector:
V = [ 7 6 2 9 2]
[~,r] = sort(V)
rankV(r) = 1:numel(V)
for a matrix, you can loop over the columns
M = magic(5)
[~,r] = sort(M)
szM = size(M)
rankM = zeros(szM) % pre-allocation
ridx = 1:szM(1)
for k=1:szM(2)
rankM(r(:,k),k) = ridx
end
Other approaches using, for instance, ndgrid and sub2ind are also fine but less readable, I think.

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