how can i write this matrix in matlab?

how can i write this matrix in matlab? this matrix is (n+1)*(n+1) that n must be enter by user

Answer 1

[Rick Rosson]

x = zeros(n+1);
x(1,1:2) = [ 2 1 ];
x(end,end-1:end) = [ 1 2 ];

for k = 2:n
    x(k,k–1:k+1) = [ 1 4 1 ];
end

Answer 2

[dpb]

Given input n and

r = [1     4     1];

c={repmat(r,n,1)};             % cell array of n copies of r
m=blkdiag([2 1],c{:},[1 2]);   % expand c to comma list for blkdiag
clear c

Answer 3

[Image Analyst]

Lots of ways, for loop, addition, assignment, zeros(), etc. I'd probably use eye() and circshift(). Hint:

diagArray = 4 * eye(7)

See what that gives you. Imagine shifting some diagonal arrays with circhsift() and adding the 3 arrays together. That should be enough hint to get you started.

[dpb]

I thought the blkdiag solution kinda' cute, IA... :)

Excepting for needing the temporary cell array; couldn't see a simple way to generate the comma-separated list in one swell foop...