vectorize expression containing if statement
2 visualizzazioni (ultimi 30 giorni)
Mostra commenti meno recenti
A = [-5 3 2;2 3 4; 3 5 6; -2 8 9];
%compute product of columns in a vectorized fashion
A(:,1).*A(:,2).*A(:,3);
%calculate the above product only for the rows where the entry in the first column is positive
%solution I do not like. A is not needed anymore after the calculation
A(~(A(:,1)>0),:) = [];
A(:,1).*A(:,2).*A(:,3)
Is there a way to get the above 2x1 result vector using one single line of code? I would also be happy with a 4x1 vector that contains NaN when the condition is not met. The issue is that my real A is quite large in size, so I want to be as efficient as possible and avoiding unnecessary copies or temporary variables related to the condition.
0 Commenti
Risposta accettata
the cyclist
il 13 Lug 2023
Modificato: the cyclist
il 13 Lug 2023
Here is one way:
A = [-5 3 2;2 3 4; 3 5 6; -2 8 9];
prod(A(A(:,1)>0,:),2)
You could also have done the first operation as
prod(A,2)
2 Commenti
the cyclist
il 14 Lug 2023
This question is so different from what you oringally asked, that I'm wary of what is important.
Can't you just do
if det(M) > 0
<do the trace operation on M here>
end
?
If that isn't right, can I suggest you post a new question (because what you actually asked here was answered). You can upload your matrix using the paper clip icon in the toolbar, and then people can test code for speed on your actual data.
Più risposte (0)
Vedere anche
Categorie
Scopri di più su Operating on Diagonal Matrices in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!