Question related to vectorized matrix operation.
1 vue (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Pappu Murthy
le 22 Jan 2017
Modifié(e) : Pappu Murthy
le 23 Jan 2017
i have two matrices A and B; A is say (Nx3) where N is rather large like 1000+... B is (nx2) where n is rather smaller of the order 10 or so.. but it does not matter it is smaller than A row size. i would like to compute
for i = 1:N
D = ( A(i,1)- B(1:n,1) )^2 + (A(i,2) - B(1:n,2)^2 )
end
for e.g. if N is 4, and n =2 then D = a [4x2] matrix...
I am able to perform this using for loops without much difficulty but would like to try using the vectorized Matrix operations instead for improving the performance and speed. Thanks in advance.
0 commentaires
Réponse acceptée
Stephen23
le 22 Jan 2017
Modifié(e) : Andrei Bobrov
le 23 Jan 2017
>> A = randi(9,4,3)
A =
4 2 9
9 4 4
5 4 8
4 2 8
>> B = randi(9,3,2)
B =
3 2
6 4
3 1
>> D = bsxfun(@minus,A(:,1),B(:,1).').^2 + bsxfun(@minus,A(:,2),B(:,2).').^2
D =
1 8 2
40 9 45
8 1 13
1 8 2
4 commentaires
Plus de réponses (1)
Andrei Bobrov
le 23 Jan 2017
Modifié(e) : Andrei Bobrov
le 23 Jan 2017
My variants:
For R2016b and later
>> C2 = squeeze(sum((A(:,1:2) - permute(B,[3,2,1])).^2,2))
C2 =
1 8 2
40 9 45
8 1 13
1 8 2
and with bsxfun:
>> C3 = squeeze(sum(bsxfun(@minus,A(:,1:2),permute(B,[3,2,1])).^2,2))
C3 =
1 8 2
40 9 45
8 1 13
1 8 2
1 commentaire
Voir également
Catégories
En savoir plus sur Matrix Indexing 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!