Creating a 4-D array

Hello everyone, I have been having trouble understanding the syntax behind creating 4-D matrices and I was hoping someone can answer my query.

I need to create a 4D matrix from my matlab data so I can use it as an input to another software which uses only 4D inputs. The matrix looks like this,

4-d_matrix=[time; 3-component_velocity; x_grid; y_grid]

Where time is of the size (1,n) 3-component velocity is of the size (l*b,3) and x_grid and y_grid correspond to the grid size which is l and b for x and y (l=b).

[Stephen23]

 4-d_matrix=[time; 3-component_velocity; x_grid; y_grid]

That syntax does not create a 4D array, and there is not reason to believe that it would. That syntax creates a 2D matrix, as the documentation clearly explains:

https://www.mathworks.com/help/matlab/math/creating-and-concatenating-matrices.html

https://www.mathworks.com/help/matlab/learn_matlab/matrices-and-arrays.html

To create a 4D array you will need to use indexing, reshape, permute, or something of that ilk.