def reflectivity(self):
"""
The reflectivity of the sampled system
"""
rerr = np.sqrt(self.reflected_beam)
ierr = np.sqrt(self.direct_beam)
dx = np.sqrt((self.dlambda)**2 + self.dtheta**2 + self.rebin**2)
ref, rerr = ErrorProp.EPdiv(self.reflected_beam, rerr,
self.direct_beam, ierr)
dataset = ReflectDataset(data=(self.q, ref, rerr, dx * self.q))
# apply some counting statistics on top of dataset otherwise there will
# be no variation at e.g. critical edge.
return dataset.synthesise()
