TukeyBiweight.psi()

statsmodels.robust.norms.TukeyBiweight.psi

TukeyBiweight.psi(z) [source]

The psi function for Tukey’s biweight estimator

The analytic derivative of rho

Parameters:

Parameters:	z : array-like 1d array
Returns:	psi : array psi(z) = z(1 - (z/c)2)*2 for \|z\| <= R psi(z) = 0 for \|z\| > R

z : array-like

1d array

Returns:

psi : array

psi(z) = z*(1 - (z/c)**2)**2 for |z| <= R

psi(z) = 0 for |z| > R

© 2009–2012 Statsmodels Developers
© 2006–2008 Scipy Developers
© 2006 Jonathan E. Taylor
Licensed under the 3-clause BSD License.
http://www.statsmodels.org/stable/generated/statsmodels.robust.norms.TukeyBiweight.psi.html