HESS

 

 Hessenberg form.

  The Hessenberg form of a matrix is zero below the first

  subdiagonal. If the matrix is symmetric or Hermitian,

  the form is tridiagonal.  [P,H] = HESS(A) produces a unitary

  matrix P and a Hessenberg matrix H so that A = P*H*P' and

  P'*P = EYEMO0DU2(P).  By itself, HESS(A) returns H.