CODEWITHSUNDEEP
matlab
Christina
Christina

Reputation: 935

Creating a 3 dimensional matrix from a matrix and vector in MATLAB

I have a matrix A of size p x p and a vector y = [y1,y2,...,yn].

What do I want to do is to create a 3 dimensional matrix of size p x p x n, that is, it contains n bands where each one is of size p x p.

How each band is created?:

Each band is equal to the matrix A multiplied by one value in y. For example, the first band is A * y1, the second band is A * y2. On the other hand, the band number i, where i = 1, ..., n, is equal to A * yi

Well, this can be easily done using a for loop, but this is trivial and expensive in computation. How can I prevent using a for loop? Is there any very fast automatic method that can directly create the 3-D matrix?

Any help will be very appreciated.

Upvotes: 0

Views: 85

Answers (1)

Suever
Suever

Reputation: 65430

You can use bsxfun to multiply your p x p matrix by each value in y. We must reshape y to be 1 x 1 x n though so that the multiplication creates a third dimension.

out = bsxfun(@times, A, reshape(y, 1, 1, []));

If you're on R2016b or newer (when MATLAB introduced implicit broadcasting), you can replace bsxfun with simply .*

out = A .* reshape(y, 1, 1, []);

Upvotes: 2

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