Trying to form a large matrix from 1 small matrix

Here is the code:

clear all

clc

syms s x

he = 1/22

k_e = [12/(he^3) 12/(he^3) 6/(he^2) 6/(he^2);

12/(he^3) 12/(he^3) -6/(he^2) -6/(he^2);

6/(he^2) -6/(he^2) 4/(he^2) 2/(he^2);

6/(he^2) -6/(he^2) 2/(he^2) 4/(he^2)];

k_g = zeros(46)

for r = 1:23

for c = 1:23

if c = 21

continue

end

if r = 21

continue

end

k_g(r+2,c+2) = k_e;

end

end

k_g

The aim is to insert k_e in k_g after 2 rows and 2 columns and sum the merging values

By "sum mergin vaues", I mean that first time k_e is in k_g, it takes 1,1 to 4,4.

The next time, k_e is inserted starting from 3,3 position and the values at 3,3 3,4 4,3 4,4 are summed with the previous k_e in k_g.

Just as an example, a 2x2 (k_e) which looks like this:

a = [A B C;

D E F;

G H I];

Which added again and again in to b should look like this:

b = [A B C 0 0 0 0;

D E F 0 0 0 0;

G H I+A B C 0 0;

0 0 D E F 0 0;

0 0 G H I+A B C;

0 0 0 0 D E F;

0 0 0 0 G H I];

I hope it clarifies the problem.

Only this time, the a is a 4x4 and b is 46x46 and a is inserted at every (n+2)th row and (n+2)th column

Thanks

Answer 1

[Alex Hanes]

If I’m following correctly, the following code should get you in the right direction:

k_e = 2*ones(4,4);    % place-holder for your symbolic ke
dimB = 46;            % set dimension of B-array
B0   = zeros(dimB);   % pre-allocate
B    = zeros(dimB);   % pre-allocate
[m,n] = size(k_e); 
B0(1:m,1:n) = k_e;    % store k_e in first position
for k = 0:2:dimB-m 
    B = B + circshift(circshift(B0,k,1),k,2); 
end