Test the validity of a stiffness matrix
wrong_struct = rank_efficient_struct(K,p,e)
the stiffness matrix of the structure (computed via a call to femtruss)
a matrix containing the coordinate of the points. It's a npoints x 2 matrix for a 2 dimensions structure and a npoints x 3 for a 3 dimensions structure.
a matrix containing the list of fixed degrees of freedom.
%T
if the structure produces a stiffness matrix which is not
of full rank (this can mean that some bars are missing).
Test the validity of a stiffness matrix