Create a 3D matrix

Question

How can I define a 3D matrix in MATLAB?

For example a matrix of size (8 x 4 x 20) or add a 3rd dimension to an existing 2D matrix?

Answer 1

I use Octave, but Matlab has the same syntax.

Create 3d matrix:

octave:3> m = ones(2,3,2)
m =

ans(:,:,1) =

   1   1   1
   1   1   1

ans(:,:,2) =

   1   1   1
   1   1   1

Now, say I have a 2D matrix that I want to expand in a new dimension:

octave:4> Two_D = ones(2,3)
Two_D =
   1   1   1
   1   1   1

I can expand it by creating a 3D matrix, setting the first 2D in it to my old (here I have size two of the third dimension):

octave:11> Three_D = zeros(2,3,2)
Three_D =

ans(:,:,1) =

   0   0   0
   0   0   0

ans(:,:,2) =

   0   0   0
   0   0   0



octave:12> Three_D(:,:,1) = Two_D
Three_D =

ans(:,:,1) =

   1   1   1
   1   1   1

ans(:,:,2) =

   0   0   0
   0   0   0