Addtion with 2x1 Vector and 2x3 Matrix
2 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hi,
In the 2017a documentation, I find that you can "Create an array, A, and add a column vector to it. The vector is treated as though it is a matrix of the same size as A, so that each element in the vector is added to a row in A."
https://www.mathworks.com/help/matlab/ref/plus.html
I am using an older release of Matlab (2015a) and this operation does not work for me. I get the following error:
Error using + Matrix dimensions must agree.
Can anyone tell me how to perform this operation on an older release, and exactly which release was this new functionality available?
Thanks
0 commentaires
Réponse acceptée
Jan
le 21 Mar 2017
Modifié(e) : Jan
le 21 Mar 2017
The new method was introduced in R2016b. See e.g. Loren: arithmetic-expanding. Use bsxfun for older Matlab versions:
A = rand(2, 3)
b = rand(2, 1)
R1 = bsxfun(@plus, A, b) % Matlab < 2016b
R2 = A + b % Matlab >= 2016b
bsxfun was introduced in 2007a. Before the array way expaned by repmat or ones:
R3 = A + b(:, ones(1, 3))
R4 = A + repmat(b, [1, 3])
The ones-method was processed efficiently by Matlab's JIT acceleration: The timings looked like Matlab does not waste time with creating the expanded array explicitely, but the addition was performed directly. But this is an assumption only: The JIT was never documented exactly.
6 commentaires
Steven Lord
le 21 Mar 2017
In the section for release R2016b it's the first item in the Mathematics subsection. It's called implicit expansion.
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Matrices and Arrays dans Help Center et File Exchange
Produits
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!