Matlab: How to multiply 3-dimensional array with Vector?

Question

Suppose I have an array M of dimension M = (3, 12, 9) and a vector C with 9 elements.

How do I efficiently multiply M with C so that

M(:,:,1) * C(1)
M(:,:,2) * C(2)

and so forth?

help is much appreciated. Thanks in advance

Do you want to perform scalar multiplication ? Because `M(:,:,1)` is a `3x12` matrix whereas `C(1)` is a single element. — articuno, Apr 06 '15 at 12:21
http://stackoverflow.com/questions/5681196/3d-matrix-multiplication-with-vector — Charly, Apr 06 '15 at 12:21
You asked the same question not 2 weeks ago: http://stackoverflow.com/questions/29276924 ??? — knedlsepp, Apr 06 '15 at 19:01

score 1 · Answer 1 · edited May 23 '17 at 10:24

1

Code:

bsxfun(@times,A,permute(C(:),[3 2 1]));

orginally answered by Divakar taken from here

edited May 23 '17 at 10:24

Community

answered Apr 06 '15 at 12:22

Santhan Salai

I want to scale each individual 3,12 submatrix with the corresponding value in C. @Santhan, I dont get how this is suppose to help... can you elaborate? – CD86 Apr 06 '15 at 12:25
Edited. See the link mentioned. – Santhan Salai Apr 06 '15 at 12:27
2

Would be nice to mention the assumption that vector C is a row vector, or do `bsxfun(@times,A,permute(C(:).',[3 1 2]));` or `bsxfun(@times,A,permute(C(:),[3 2 1]));` without stating any assumption. – Divakar Apr 06 '15 at 12:48
thanks a lot but here is a follow up question: Suppose I have a matrix M = (3, 12, 4) and I want to transform it so that M = (12,12) basically just concatenating the individual (3,12) submatrices under each other. How do I do that? Thanks in advance – CD86 Apr 06 '15 at 12:52
1

@CarstenD That "concatenating under each other" operation is also dealt with in that [other answer](http://stackoverflow.com/a/23808285/3293881) at the end of it. – Divakar Apr 06 '15 at 12:55
@CarstenD see [reshape](http://in.mathworks.com/help/matlab/ref/reshape.html?refresh=true) – Santhan Salai Apr 06 '15 at 12:57
@Divakar, I'm a begginer and didn't knew `anyVector(:)` will always return a column vector. Its great to know. Thanks once again for pointing and correcting :) – Santhan Salai Apr 06 '15 at 13:18

1 Answers1