matrix automation problem

[c21 c11 c21 0 0 0 0 0 0 0; 0 c21 c11 c21 0 0 0 0 0 0; 0 0 c21 c11 c21 0 0 0 0 0; 0 0 0 c21 c11 c21 0 0 0 0; 0 0 0 0 c21 c11 c21 0 0 0; 0 0 0 0 0 c21 c11 c21 0 0; 0 0 0 0 0 0 c21 c11 c21 0; 0 0 0 0 0 0 0 c21 c11 c21] where the amount of rows/columns depends on a variable m and n respectively m=n-2

and n=10 in this case

how do i "automate" this??? TIA

Answer 1

[Richard Brown]

This is one annoying case where the sparse version spdiags can do more than the full one diag

n = 10;
m = n-2;
c11 = 1;
c21 = 2;

B = repmat([c21 c11 c21], m, 1);
A = spdiags(B, [0 1 2], m, n);

You might want to use

A = full(spdiags(B, [0 1 2], m, n));

if you don't want a sparse matrix.