= ( Z ) P,  M &lt; N,
                                   ( R )

  (RQ factorization), where P is an M-by-M orthogonal matrix and
  R is a square upper triangular matrix.

  These factorizations are used to solve the continuous-time
  Lyapunov equation in the canonical form
                                                     2
    op(A)'*op(U)'*op(U) + op(U)'*op(U)*op(A) = -scale *op(F)'*op(F),

  or the discrete-time Lyapunov equation in the canonical form
                                                  