lqqPsi: Default lqq (linear-quadratic-quadratic) redescending...

In robustlmm: Robust Linear Mixed Effects Models

Default lqq (linear-quadratic-quadratic) redescending psi-function.

Description

Pre-built psi_func_rcpp from makeRobustbasePsi("lqq") with robustbase's default lqq tuning (about 95% efficiency at the normal). The lqq psi of Koller and Stahel (2011) redescends more gradually than the bisquare and is the recommended redescender, as used by robustbase's lmrob.control(setting = "KS2014"). Use it as rho.e in rlmer; a redescender needs a good initial estimate, so pair it with init = "ransac" or rlmer_ransac.

References

Koller, M. and Stahel, W. A. (2011) Sharpening Wald-type inference in robust regression for small samples. Computational Statistics & Data Analysis 55(8), 2504–2515.

See Also

makeRobustbasePsi, bisquarePsi.

robustlmm documentation built on July 30, 2026, 5:11 p.m.