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

User · Answer

I use Octave  but Matlab has the same syntax   Create 3d matrix   octave 3 gt  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 gt  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 gt  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 gt  Three D     1    Two D Three D    ans     1        1   1   1    1   1   1  ans     2        0   0   0    0   0   0

User · Answer

If you want to define a 3D matrix containing all zeros  you write  A   zeros 8 4 20     All ones uses ones  all NaN s uses NaN  all false uses false instead of zeros   If you have an existing 2D matrix  you can assign an element in the  3rd dimension  and the matrix is augmented to contain the new element  All other new matrix elements that have to be added to do that are set to zero   For example  B   magic 3      creates a 3x3 magic square B 2 1 2    1     and you have a 3x3x2 array

User · Answer

Create a 3D matrix  A   zeros 20  10  3        Creates a 20x10x3 matrix   Add a 3rd dimension to a matrix  B   zeros 4 4     C   zeros size B 1   size B 2   4       New matrix with B s size  and 3rd dimension of size 4 C     1    B                            Copy the content of B into C s first set of values   zeros is just one way of making a new matrix  Another could be A 1 20 1 10 1 3    0 for a 3D matrix  To confirm the size of your matrices you can run  size A  which gives 20 10  3   There is no explicit bound on the number of dimensions a matrix may have

[matlab] Create a 3D matrix

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