class statsmodels.robust.norms.RobustNorm[source]

The parent class for the norms used for robust regression.

Lays out the methods expected of the robust norms to be used by statsmodels.RLM.


None :

Some subclasses have optional tuning constants.

See also

statsmodels.rlm, and


Currently only M-estimators are available.


PJ Huber. ‘Robust Statistics’ John Wiley and Sons, Inc., New York, 1981.

DC Montgomery, EA Peck. ‘Introduction to Linear Regression Analysis’,
John Wiley and Sons, Inc., New York, 2001.
R Venables, B Ripley. ‘Modern Applied Statistics in S’
Springer, New York, 2002.


psi(z) Derivative of rho.
psi_deriv(z) Deriative of psi.
rho(z) The robust criterion estimator function.
weights(z) Returns the value of psi(z) / z