how to use bsxfun or arrayfun to build the following matrix
3 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hi, there.
I want to use bsxfun or arrayfun to replace the following for loop.
for s=1:S
New_P(s,:)=P(s,:,U0(s));
end;
for example,
if P(:,:,1)=[1,2;3,4];
P(:,:,2)=[5,6;7,8];
U0=[1;2];
then the final result is New_P=[1,2;7,8];
Thank you in advance!
2 commentaires
Adam
le 25 Fév 2016
Is there any particular reason why you want to use arrayfun or bsxfun? arrayfun is generally slower than a for loop and is also more suited to 1d arrays than multidimensional arrays. It can certainly be used for multidimensional arrays, but it effectively just interprets it as a 1d array anyway using linear indexing on the array.
I'm not aware of a syntax of bsxfun that would be useful for this, though maybe it is. I use it for certain specific tasks so haven't used all its capabilities.
Réponse acceptée
Guillaume
le 25 Fév 2016
P = cat(3, [1 2;3 4], [5 6;7 8]);
U0 = [1;2];
New_P = P(sub2ind(size(P), ...
repmat((1:size(P, 1))', 1, size(P, 2)), ... rows where to pick the elements
repmat(1:size(P, 2), size(P, 1), 1), ... columns where to pick the elements
repmat(U0, 1, size(P, 2)))) %pages where to pick the elements
1 commentaire
Guillaume
le 25 Fév 2016
Note that you could generate the rows and columns matrix with ngrid if you prefer:
[rows, cols] = ndgrid(1:size(P, 1), 1:size(P, 2));
new_P = P(sub2ind(size(P), rows, cols, repmat(U0, 1, size(P, 2))))
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Creating and Concatenating Matrices dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!