statsmodels.robust.norms.RamsayE.rho¶ RamsayE.rho(z)[source]¶ The robust criterion function for Ramsay’s Ea. Parameters:¶ z : array_like¶1d array Returns:¶ rho – rho(z) = a**-2 * (1 - exp(-a*|z|)*(1 + a*|z|)) Return type:¶ ndarray