How do I combine four 3x3 matrices into a 6x6 matrix?

Suppose I have the matrices

A=[1 1 1

1 1 1

1 1 1]

B=[2 2 2

2 2 2

2 2 2]

C=[3 3 3

3 3 3

3 3 3]

D=[4 4 4;

4 4 4;

4 4 4]

I need the combined matrix to be,

New=[ 1 1 1 2 2 2

1 1 1 2 2 2

1 1 1 2 2 2

3 3 3 4 4 4

3 3 3 4 4 4

3 3 3 4 4 4]

I could write a loop and combine it as such but I would likle to know if there are any functions that could do the same!!

Answer 1

[Davide Masiello]

If it's really only 4 matrixes, then I would just write

New = [[A,B];[C,D]];

If the code needs to be expanded for a larger number of matrixes then it may be convenient to use a loop, but you should specify how those matrixes must be arranged to form the new one.

[Stephen23]

The simpler MATLAB approach:

New = [A,B;C,D];

"If the code needs to be expanded for a larger number of matrixes then it may be convenient to use a loop"

The MATLAB approach would be to use CELL2MAT or a comma-separated list with CAT or [].

[Davide Masiello]

@Stephen thanks for your comment. When I suggested a loop I thought of something like concatenating a large number of matrixes. If that was the case, a loop might still be needed to create the cell array to pass to cell2mat I guess. But please let me know if I am missing something.

[Stephen23]

"When I suggested a loop I thought of something like concatenating a large number of matrixes"

Using a loop to concatenate (and enlarge) an array on each loop iteration is very inefficient. Much better approaches would be to use indexing to allocate the data to a preallocated array, or use a comma-separated list with CAT or [].

[Rakshith M]

Thanks for the help!!