function A = gen_der2_mat(n)
% GEN_DER2_MAT - Generates the matrix (of size nxn) representing the second derivative operator
% 
% Written by:
% -- 
% John L. Weatherwax                2006-12-20
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

A = diag( 2*ones(1,n), 0 ) + diag( -1*ones(1,n-1), -1 ) + diag( -1*ones(1,n-1), +1 );