MATLAB: How to multiply a NNM matrix with 1*M array

arraymatrix arraymatrix manipulationmultiple

I have a matrix A with size N*N*M and array b with the size of 1*M.

I want to multiply the elements of i^th dimension of matrix A (i.e. A(:,:,i) ) with the i^th dimension of array b (i.e. b(1,i)). Meaning that: e.g.:

A(:,:,1)=[1 1; 1 1]
A(:,:,2)=[1 1; 1 1]
A(:,:,3)=[1 1; 1 1]
b=[1 2 3]
=> A times b
Results:
C(:,:,1)=[1 1; 1 1]
C(:,:,2)=[2 2; 2 2]
C(:,:,3)=[3 3; 3 3]

I am not looking for writing a loop and go through every single layer separately.

I was wondering if you guys know a fast way to do it. Thanks

Best Answer

This works correctly, and is fast and efficient:

A(:,:,1)=[1 1; 1 1];
A(:,:,2)=[1 1; 1 1];
A(:,:,3)=[1 1; 1 1];
b=[1 2 3];
bsxfun(@times,A,reshape(b,1,1,[]))

Related Solutions

MATLAB: Matrix Manipulation

A = [1; 1; 3; 1; 2; 1; 1; 1; 3; 1; 1; 1; 1; 2; 1; 1; 1; 1; 1; 3; 1; 1; 1; 2; 1; 1; 1; 1; 1; 2; 2; 1; 1; 1; 2; 1; 1; 2; 1; 1; 1; 1; 1; 1; 3; 1; 1; 3; 2; 1; 1; 1; 1; 1; 1; 1; 2; 2; 4; 1; 1; 2; 1; 1; 1; 1; 2; 2; 1; 1; 1; 3];
a1=find(A==2)-1; %find the index of the 2
a2=find(A==3)-1; %find the index of the 3
a2=repmat(a2,2,1) %duplicate the 3 indexes
B=sort([a1;a2])'; %join and sort the solution, also transpose
%I transposed B because of your B example

MATLAB: Superimpose matrices (n,n,m) to (n,n,1)

Here are some options.

Compute and plot the maximum value at each pixel:

imagesc(max(a100,[],3))

Compute and plot the minimum value at each pixel:

imagesc(min(a100,[],3))

Compute and plot the sum of all the images:

imagesc(sum(a100,3))

Compute and plot the average of all the images:

imagesc(mean(a100,3))

Best Answer

Related Solutions

MATLAB: Matrix Manipulation

MATLAB: Superimpose matrices (n,n,m) to (n,n,1)

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