NxN matrix with 2s on main diagonal

How do I create NxN matrix which has 2s on main diagonal, -1s on diagonal above and below 2s and -1 last element (Nth) in the first row and first element in Nth row.

[KSSV]

You can create using diag. Doc diag.

Answer 1

[Guillaume]

N = 8;  %e.g.
m = full(gallery('tridiag', N));
m([N, (N-1)*N+1]) = -1

[ieva ashmore]

thank you! It surely works

[ieva ashmore]

Guillaume, Just out of pure interest can you expand on m([N, (N-1)*N+1]) = -1 I see that it could have been done with two commands m(1,N)=-1 and m(N,1)=-1 But I would like to learn more about the method you have used Thanks

[Sean de Wolski]

He's using linear indexing. https://www.mathworks.com/help/releases/R2016b/matlab/math/matrix-indexing.html

Answer 2

[Andrei Bobrov]

toeplitz([2 -1 zeros(1,n-3) -1])