function?[stiffness]=...
formStiffness2Dtruss（GDofnumberElements...
elementNodesnumberNodesnodeCoordinatesxxyyEA）;
stiffness=zeros（GDof）;
%?computation?of?the?system?stiffness?matrix
for?e=1:numberElements;
%?elementDof:?element?degrees?of?freedom?（Dof）
indice=elementNodes（e:）?;
elementDof=[?indice（1）*2-1?indice（1）*2?indice（2）*2-