def gaussGrad(self): r""" Return :math:`\frac{1}{V_P} \sum_f \vec{n} \phi_f A_f` as a rank-1 `CellVariable` (first-order gradient). """ if not hasattr(self, '_gaussGrad'): from fipy.variables.gaussCellGradVariable import _GaussCellGradVariable self._gaussGrad = _GaussCellGradVariable(var = self, name = "%s_gauss_grad" % self.name) return self._gaussGrad