function stif=asmstf(x,y,Area,Emod,inode,jnode)
%
% stif=asmstf(x,y,Area,Emod,inode,jnode)
% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% This function assembles the global stiffness 
% matrix for a plane truss structure.  The 
% stiffness matrix has an order equal to twice 
% the number of nodes.
%
% x,y         - global nodal coordinate vectors
% Area        - member area vector
% Emod        - modulus of elasticity vector
% inode,jnode - indices of the member ends
%
% stif - global stiffness matrix
%
% User m functions called:  elmstf
%----------------------------------------------

numnod=length(x); numelm=length(Area);
i=inode(:); j=jnode(:);
stif=zeros(2*numnod); ij=[2*i-1,2*i,2*j-1,2*j];
%...Place the stiffness matrix for individual 
%...members at proper positions in the global 
%...matrix
for k=1:numelm, kk=ij(k,:);
  stif(kk,kk)=stif(kk,kk)+ ...
    elmstf(x,y,Area(k),Emod(k),i(k),j(k));
end