# How can I make a variant submatrix?

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Felipe Ribas on 22 Oct 2020
Commented: Vijay on 22 Oct 2020
Hello everybody,
Does anyone know how I can make a variant submatrix, for example, if I have a matrix A (100,100) use a submatrix B (10,10) to get the first 10 rows and 10 columns, then the next 10 columns so on until all elements of the columns and rows have been taken.

Vijay on 22 Oct 2020
You could try below
(1) If you are just aiming to the get the submatrices in the diagonal of A...
I = length(A);
n = 10; % size of the desired squared submatrix
i= I/n;
% s1 = 'B';
% s2 =[1:i];
for j=1:i
% s3=num2str(s2(j));
eval(sprintf('B%d = A((j-1)*n+1:n*j,(j-1)*n+1:n*j)', j));
end
(2) If you are aiming to cover all the rows and columns...
I = length(A);
n = 10; % size of the desired squared submatrix
i= I/n;
for j=1:i
for k=1:i
eval(sprintf('B%d = A((j-1)*n+1:n*j,(k-1)*n+1:n*k)', (j-1)*i+k));
end
end

#### 1 Comment

Vijay on 22 Oct 2020
*Note: This code works only if your reference matrix is a square matrix

You can use vectors to point to the indices of matrix A,
For example:
A(1:10, 1:10); % the first one
A(11:20, 1:10) % second submatrix
A(21:30, 1:10)
%...
A(91:100, 1:10);
A(1:10, 11:20 ...
% ...
A(91:100, 91:100);
% you need to have a loop to go through all sub matrices