function x = u2d_to_1d(m,u)

% This subroutine transform a two dimensional vector u(1:m+1,1:n+1)
% to a one dimensional verctor x((m-1)*(n-1)) in the order of
% (2,2), (3,2), ..., (m-1,2), (2,3), (2,4), ... (m-1,n-1).

x = zeros((m-1)*(m-1),1);
for j=2:m
   for i=2:m,
     k = (j-2)*(m-1) + i-1;
     x(k) = u(i,j);
   end
end