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

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HOEMIN
HOEMIN 2013-11-18
评论： Simon 2013-11-19
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...

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采纳的回答

Sean de Wolski
Sean de Wolski 2013-11-18
编辑：Sean de Wolski 2013-11-18
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

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Simon
Simon 2013-11-18
  3 个评论
显示 1更早的评论
Simon
Simon 2013-11-18
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];

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