Matrix extension by inserting 0

I want to extend matrix by inserting 0 like uploaded picture.

How can I do?

Answer 1

[Voss]

k2 = 1;
M1 = [k2 -k2 -k2 k2; 0 k2 k2 -k2; 0 0 k2 -k2; 0 0 0 k2];

M1_new = zeros(size(M1)+2);
M1_new([1 2 5 6],[1 2 5 6]) = M1;

disp(M1);

     1    -1    -1     1
     0     1     1    -1
     0     0     1    -1
     0     0     0     1

disp(M1_new);

     1    -1     0     0    -1     1
     0     1     0     0     1    -1
     0     0     0     0     0     0
     0     0     0     0     0     0
     0     0     0     0     1    -1
     0     0     0     0     0     1

k3 = 1;
M2 = [k3 0 -k3 0; 0 0 0 0; -k3 0 k3 0; 0 0 0 0];

[m,n] = size(M2);
M2_new = zeros(m+2,n+2);
M2_new(1:m,1:n) = M2;

disp(M2);

     1     0    -1     0
     0     0     0     0
    -1     0     1     0
     0     0     0     0

disp(M2_new);

     1     0    -1     0     0     0
     0     0     0     0     0     0
    -1     0     1     0     0     0
     0     0     0     0     0     0
     0     0     0     0     0     0
     0     0     0     0     0     0

Answer 2

[dpb]

M1=eye(4);                                      % simply symmetric matrix to play with
N=2;                                            % number columns/rows to insert
R=2;C=2;                                        % starting row, column at which to insert
Z=zeros(size(M1,1),N);                          % zeros columns to insert; could be anything constant
M2=[M1(:,1:C) Z M1(:,C+1:end)];                 % step 1; insert the columns
M2=[M2(1:R,:); [Z.' zeros(N)]; M2(R+1:end,:)];  % step 2; insert rows; must augment the Z to match new

The latter is quite simple to just place the original in the corner of a larger -- but there is a MATLAB syntax "trick" -- start with M1 again, then--

S=size(M1); S=S+N;                              % get size vector, augment to desired size
M2=M1;                                          % start with original
M2(S(1),S(2))=0;                                % set outer bound value; ML automagically zero extends