How to make the main diagonal and the diagonal above and below the main diagonal equal to -2 and 1 respectively

Hi, I have a NxN matrix (N=100) how can I make it so that the main diagonal is -2 and the diagonal above and below the main is 1? and everything else is 0? thanks!

[madhan ravi]

[ -2  1   1;... where would you put zero??
   1  -2  1;...
   1  1  -2]

[JONATHAN NEMARIAM]

Well the matrix would be 100x100, so the diagonal would be -2 and ONLY the diagonal above and below the main will be 1, so everything else will be a 0.

[-2 1 0 0 0 0 0

1 -2 1 0 0 0 0

0 1 -2 1 0 0 0

0 0 1 -2 1 0 0] and so on to where it's 100x100

[Takumi]

N = 100;
A = -2*eye(N) + diag(ones(1,N-1),1) + diag(ones(1,N-1),-1);

Answer 1

[Andrei Bobrov]

A = gallery('tridiag',100,-1,2,-1);

or

n = 100;
A = spdiags(ones(n,1)*[-1 2 -1],-1:1,n,n);