Arrange the matrix by replace a part to another part

Hi

I have 4 matrices as example, I would like to arrange these matrices to be one big matrix after keep only (the beginning of rows and columns) as this example

If I have

A1=ones(12);
A2=ones(9)*2;
A3=ones(6)*3;
A4=ones(4)*4;

I would like to find the final matrix after keep only the first 3 (the beginning of rows and columns in each matrix ) , so the final matriix should be like

ATOT=
[1	1	1	1	1	1	1	1	1	1	1	1
1	1	1	1	1	1	1	1	1	1	1	1
1	1	1	1	1	1	1	1	1	1	1	1
1	1	1	2	2	2	2	2	2	2	2	2
1	1	1	2	2	2	2	2	2	2	2	2
1	1	1	2	2	2	2	2	2	2	2	2
1	1	1	2	2	2	3	3	3	3	3	3
1	1	1	2	2	2	3	3	3	3	3	3
1	1	1	2	2	2	3	3	3	3	3	3
1	1	1	2	2	2	3	3	3	4	4	4
1	1	1	2	2	2	3	3	3	4	4	4
1	1	1	2	2	2	3	3	3	4	4	4];

please i would like to specify the number of (the beginning of rows and columns) that should keep because i have diffrent size of matrices

thank you very much

[Aakash Deep Chhonkar]

Try indexing the matrix, https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

Also, focus on which part of the matrix you want to update rather than which part you want to preserve, this will clear the picture more.

[mohammed hussein]

thank you

Answer 1

[Scott MacKenzie]

Assuming your matrices are conveniently sized...

A1=ones(12);
A2=ones(9)*2;
A3=ones(6)*3;
A4=ones(3)*4;

A = A1;
A(4:end,4:end) = A2;
A(7:end,7:end) = A3;
A(10:end,10:end) = A4

Output:

A =

1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 1

1 1 1 2 2 2 2 2 2 2 2 2

1 1 1 2 2 2 2 2 2 2 2 2

1 1 1 2 2 2 2 2 2 2 2 2

1 1 1 2 2 2 3 3 3 3 3 3

1 1 1 2 2 2 3 3 3 3 3 3

1 1 1 2 2 2 3 3 3 3 3 3

1 1 1 2 2 2 3 3 3 4 4 4

1 1 1 2 2 2 3 3 3 4 4 4

1 1 1 2 2 2 3 3 3 4 4 4

[mohammed hussein]

thank you for your answer