Filter löschen
Filter löschen

how to velocize it (avoid loop is possible)

2 Ansichten (letzte 30 Tage)
Luca Re
Luca Re am 3 Feb. 2024
Kommentiert: Matt J am 4 Feb. 2024
E=[0 5 6 9 2;0 0 1 3 1;0 5 4 2 4]'
E = 5×3
0 0 0 5 0 5 6 1 4 9 3 2 2 1 4
filtro=ones(size(E));
for i=1:width(E)
bu=find(E(:,i),1,'first');
filtro(1:bu,i)=0;
end
filtro
filtro = 5×3
0 0 0 0 0 0 1 0 1 1 1 1 1 1 1

Akzeptierte Antwort

Matt J
Matt J am 3 Feb. 2024
Bearbeitet: Matt J am 4 Feb. 2024
E=[0 5 6 9 2;0 0 1 3 1;0 5 4 2 4]';
[~,I]=max(logical(E),[],1);
filtro=(1:height(E))'>I
filtro = 5×3 logical array
0 0 0 0 0 0 1 0 1 1 1 1 1 1 1

Weitere Antworten (1)

Catalytic
Catalytic am 4 Feb. 2024
I don't know if "velocize" (not a word) is supposed to mean "accelerate" or "vectorize". The two are not the same.
If you're looking for the fastest possible code, there's no way to know in advance because it depends on the sparsity of E. For very dense E, your loop will probably be faster than @Matt J's answer.
E=rand(5000,3000)>0.1;
tic
filtro=true(size(E));
for i=1:width(E)
bu=find(E(:,i),1,'first');
filtro(1:bu,i)=0;
end
toc
Elapsed time is 0.016652 seconds.
tic
[~,I]=max(logical(E),[],1);
filtro=(1:height(E))'>I;
toc
Elapsed time is 0.031441 seconds.
  1 Kommentar
Matt J
Matt J am 4 Feb. 2024
True, but be mindful of the flipside:
E=rand(5000,3000)>0.7;
tic
filtro=true(size(E));
for i=1:width(E)
bu=find(E(:,i),1,'first');
filtro(1:bu,i)=0;
end
toc
Elapsed time is 0.051811 seconds.
tic
[~,I]=max(logical(E),[],1);
filtro=(1:height(E))'>I;
toc
Elapsed time is 0.020633 seconds.

Melden Sie sich an, um zu kommentieren.

Kategorien

Mehr zu MATLAB finden Sie in Help Center und File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by