function [k,dof] = beam2d(nodes,n1,n2,E,I,A);
%
%function [k,dof] = beam2d(nodes,n1,n2,E,I,A);
%
%  Create 2-d beam stiffness matrix
%
%  n1,n2 -- node numbers for this elem
%  nodes -- list of node coord
%  E,I,A -- modulus, moment of inertia, area
%
%  k     -- element stiffness matrix 6x6
%  dof   -- DOF list
%
error(nargchk(6,6,nargin));  %% exactly 6 inputs, please
if n1==n2
    error('Duplicate node numbers');
end