nlr (version 0.1-3)

psi.hampel: hampel redescending function

Description

• psi.hampel: compute hampel psi function.

• rho.hampel: compute hampel rho function.

Usage

psi.hampel(u, a = 1.5, b = 3.5, c = 8)
rho.hampel(u, a = 1.5, b = 3.5, c = 8)

Arguments

u

vector of values.

a

tuning constant, for wich less than that the quadratic function compute.

b

tuning constant, for wich less than that the linear function compute.

c

tuning constant, for wich less than that the constant function compute.

Value

vector of psi and who function values.

Details

psi and rho function used to in MM-estimate. The tuning constants together with k0,k1 used to give high breakdown point. This is function in MASS library, will be developed in nlr latter on.

References

Stromberg, A. J. (1993). Computation of High Breakdown Nonlinear Regression Parameters, Journal of American Statistical Association 88(421): 237-244. Stromberg, J., and Ruppert, D. (1992). Breakdown in Nonlinear Regression, Journal of American Statistical Association 87: 991-997.

See Also

rho.hampel

Examples

# NOT RUN {
## The function is currently defined as
"psi.hampel"
# }