Our professor calls this the connectivity array (but not referring to Matlab)

The goal is to combine a 3x3 matrix in a way that it becomes an 11x11 matrix. It'll be done such that the 3x3 matrix will repeat diagonally, for example if 3x3 matrix is [F G H ;

G I J;

H J F]

Then the 11x11 matrix should look like this:

[F G H 0 0 0 0 0 0 0 0;

G I J 0 0 0 0 0 0 0 0;

H J 2*F G H 0 0 0 0 0 0;

0 0 G I J 0 0 0 0 0 0;

0 0 H J 2*F G H 0 0 0 0;

0 0 0 0 G I J 0 0 0 0;

0 0 0 0 H J 2*F G H 0 0 0 0;

0 0 0 0 0 0 G I J 0 0;

0 0 0 0 0 0 H J 2*F G H;

0 0 0 0 0 0 0 0 G I J;

0 0 0 0 0 0 0 0 H J F]

notice the addition of F as a "connectivity array"

I have tried some stuff but nothing seems to work except for typing it manually and this becomes a problem if my base matrix (in this case 3x3) becomes a 10x10 or anything greater than 3x3

Answer 1

[Chunru]

%  [F G H ;
%   G I J;
%   H J F]
% Then the 11x11 matrix should look like this:
% [F G H  0 0  0  0  0  0  0 0;
%  G I J  0 0  0  0  0  0  0 0;
%  H J 2F G H  0  0  0  0  0 0;
%  0 0 G  I J  0  0  0  0  0 0;
%  0 0 H  J 2F G  H  0  0  0 0;
%  0 0 0  0 G  I  J  0  0  0 0;
%  0 0 0  0 H  J  2F G  H  0 0;
%  0 0 0  0 0  0  G  I  J  0 0;
%  0 0 0  0 0  0  H  J  2F G H;
%  0 0 0  0 0  0  0  0  G  I J;
%  0 0 0  0 0  0  0  0  H  J F]
F = 1; G = 2; H = 3; I = 4; J = 5;
A = [F G H ;  G I J;  H J F]

A = 3×3

1 2 3 2 4 5 3 5 1

B = zeros(11, 11);
for i=0:4
    B(i*2+(1:3), i*2+(1:3)) = B(i*2+(1:3), i*2+(1:3)) + A;
end
B

B = 11×11

1 2 3 0 0 0 0 0 0 0 0 2 4 5 0 0 0 0 0 0 0 0 3 5 2 2 3 0 0 0 0 0 0 0 0 2 4 5 0 0 0 0 0 0 0 0 3 5 2 2 3 0 0 0 0 0 0 0 0 2 4 5 0 0 0 0 0 0 0 0 3 5 2 2 3 0 0 0 0 0 0 0 0 2 4 5 0 0 0 0 0 0 0 0 3 5 2 2 3 0 0 0 0 0 0 0 0 2 4 5