How to change a matrix as inserting zeroes both end sides?

I wanna make 'Az2' matrix 'Az' in the picture.

This is my code for doing that,

for o=2:1:zmax-1;
  Az(o,o-1:o+1)=Az2(o,1:3);
end

however, it's way slow... Can I have any other better coding for that as using vectorization? help me...

Answer 1

[Sean de Wolski]

There's a gallery for that!

az = rand(10,3);
Az2 = full(gallery('tridiag',az(2:end,1),az(:,2),az(1:end-1,3)))

And

doc gallery

[HOEMIN]

Unbeilvable! Thanks alot. you are my life saver!

[Simon]

Hi!

But in this case Az2 is a square matrix. As I understood this was not desired?!?

Answer 2

[Simon]

Hi!

Use diag: http://www.mathworks.com/help/matlab/ref/diag.html?searchHighlight=diag

[HOEMIN]

Thanks for answer, but... that matrix is not square.

[Simon]

Hi!

It doesn't matter!

% diagonal elements
Az2 = rand(10, 3);

% diagonal 1
A1 = diag(Az2(:, 1));
A1 = [A1, zeros(size(A1, 1), 2)];
% diagonal 2
A2 = diag(Az2(:, 2), 1);
A2(end, :) = [];
A2 = [A2, zeros(size(A2, 1), 1)];
% diagonal 3
A3 = diag(Az2(:, 2), 2);
A3(end-1:end, :) = [];

% combine matrices
Az = A1 + A2 + A3;

% row with zeros in front
Az = [zeros(1, size(Az, 2)); Az];

[HOEMIN]

amazing! Thanks alot. you are my life saver!