Derivative of Tukey's bi-square loss function.

This function evaluates the first derivative of Tukey's bi-square loss function.

psi.tukey(r, k = 4.685)

Arguments

r	a vector of real numbers
k	a positive tuning constant.

Value

A vector of the same length as x.

Details

This function evaluates the first derivative of Tukey's bi-square loss function.

Author

Matias Salibian-Barrera, matias@stat.ubc.ca, Alejandra Martinez

Examples

x <- seq(-2, 2, length=10)
psi.tukey(r=x, k = 1.5)
#>  [1]  0.0000000  0.0000000 -0.2263050 -0.4293045 -0.2125747  0.2125747
#>  [7]  0.4293045  0.2263050  0.0000000  0.0000000