Split a specific matrix in 4 equal parts

If I define the matrix as follows:

Given 4 matrix of equal dimensions, say A, B, C, D.

Let

 E = [A B; C D];

May I do something like (totally pseudo-code):

 B2 = E(B);

to retrieve the submatrix B without the use of cell arrays?

Answer 1

[KSSV]

M = rand(8) ; 
[m,n]  =size(M) ; 
A = M(1:n/2,1:n/2) ; 
B = M(1:n/2,n/2+1:end) ;
C = M(n/2+1:end,1:n/2) ; 
D = M(n/2+1:end,n/2+1:end) ; 

But the best would be:

m  =size(M,1)/2 ; 
A = mat2cell(M,[m m],[m m]) ; 
A{1,1}
A{1,2}
A{2,1}
A{2,2}