Create a matrix with non zero entries on the diagonal and subdiagonal and zero elsewhere

I am confused on how to generate a 4 by 4 matrix which has ones on the diagonal and zeroes on the lower subdiagonal right beneath the diagonal and 2s on the subdiagonal right above the diagonal. In addition, there should be 0 entries elsewhere.

[James Tursa]

What have you done so far? What specific parts of your code are you having problems with?

Answer 1

[David Hill]

eye(4)+diag([2 2 2],1);