Is there faster ranking for matrices than double sort()?
1 visualización (últimos 30 días)
Mostrar comentarios más antiguos
Marin Genov
el 16 de Sept. de 2022
Editada: Marin Genov
el 16 de Sept. de 2022
I have a uint16 matrix, where I want to determine the rank of each element with respect to its column in sorted form. The sort function doesn't quite do this, but using the second output twice does it. I need to repeat this routine many times in my code, and profiling reveals that it's by far the slowest part. So, I was wondering if there is a faster way to accomplish this (double sort() seems a bit of an overkill for this perhaps).
Here is a MWE:
M = 50;
m = 50;
n = 2000;
A = randi(M,m,n,'uint16'); % generate an example matrix
% Ranking via double sort():
tic;
[~,I] = sort(A,1);
[~,R] = sort(I,1);
toc;
0 comentarios
Respuesta aceptada
Bruno Luong
el 16 de Sept. de 2022
Editada: Bruno Luong
el 16 de Sept. de 2022
Not sure it is faster, but on the theorical complexity it is better (single sort).
A = randi(10,5,3)
[~,I] = sort(A,1);
[m,n] = size(A);
R = zeros(m,n);
R(I+(0:n-1)*m) = repmat((1:m)',1,n)
9 comentarios
Bruno Luong
el 16 de Sept. de 2022
Are you sure? it looks fine to me for toy example
A = randi(10,5,3);
[~,I] = sort(A,1);
[m,n] = size(A);
% double sort
[~,R] = sort(I,1)
% accumarray
R=accumarray(reshape(I+(0:n-1)*m,[],1),repmat((1:m)',n,1),[m*n,1]); % EDIT BUG FIX
R=reshape(R,m,n)
Más respuestas (0)
Ver también
Categorías
Más información sobre Matrices and Arrays en Help Center y File Exchange.
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!