MATLAB: Combining matrices, adding two matrices in into a bigger one.

combiningmatrices

Ke1 = [ 3 3 -3 3; 3 4 -3 2; -3 -3 3 -3; 3 2 -3 4];

Ke2 = [ 6 3 -6 3; 3 2 -3 1; -6 -3 6 -3; 3 1 -3 2];

Kg = zeros(6);

Kg(1:4, 1:4) = Ke1

I also want to add Ke2 to Kg in (3:6,3:6) where they overlap in the middle but I don't know how.

Kg(3:6,3:6)=Kg(3:6,3:6)+Ke2

A =[2,6,3,1,7;9,4,2,6,3;7,1,4,5,3;7,2,5,6,3;4,2,5,3,5];
A1 = A(1:3, :);
A2 = A(4:5, :);
B = cat(1, A1, A2);  % Or [A1; A2]

These basic array operations are explained exhaustively in the Getting started chapters of the documentation.

C(:,:,1)=A+B;
c=2;
while nnz(C(:,:,end)>0)==numel(C(:,:,end))
    C(:,:,c)=C(:,:,c-1)+B;
    c=c+1;
end
C=C(:,:,1:end-1);