Tukey's Biweight

The function

(1)

sometimes used in robust estimation. It has a minimum at  and a maximum at , where

(2)

and inflection points at  and , where

(3)

REFERENCES:

Press, W. H.; Flannery, B. P.; Teukolsky, S. A.; and Vetterling, W. T. Numerical Recipes in FORTRAN: The Art of Scientific Computing, 2nd ed. Cambridge, England: Cambridge University Press, p. 697, 1992.

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