Method diagonal

include/Eigen/src/SparseCore/SparseMatrix.h:752–752

\returns a const expression of the diagonal coefficients. */

  /** \returns a const expression of the diagonal coefficients. */
  const ConstDiagonalReturnType diagonal() const { return ConstDiagonalReturnType(*this); }

  /** \returns a read-write expression of the diagonal coefficients.
   * \warning If the diagonal entries are written, then all diagonal