drc (version 1.5-2)

W1.4: The four-parameter Weibull functions

Description

'W1.4' and 'W2.4' provide the four-parameter Weibull functions, self starter function and names of the parameters.

Usage

W1.4(fixed = c(NA, NA, NA, NA), names = c("b", "c", "d", "e"))
  
  W2.4(fixed = c(NA, NA, NA, NA), names = c("b", "c", "d", "e"))

Arguments

fixed

numeric vector. Specifies which parameters are fixed and at what value they are fixed. NAs for parameter that are not fixed.

names

a vector of character strings giving the names of the parameters. The default is reasonable.

Value

• See weibull1.

Details

The equations for the mean functions are given at weibull1.

References

Seber, G. A. F. and Wild, C. J (1989) Nonlinear Regression, New York: Wiley & Sons (pp. 330--331).

See Also

Setting $c=0$ yields W1.3. A more flexible function, allowing fixing or constraining parameters, is available through weibull1.

Examples

## Fitting a four-parameter Weibull (type 1) model
terbuthylazin.m1 <- drm(rgr~dose, data = terbuthylazin, fct = W1.4())
summary(terbuthylazin.m1)