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W2

The two-parameter Weibull functions

Description

'W1.2' is the two-parameter Weibull function where the lower limit is fixed at 0 and the upper limit is fixed at 1, mostly suitable for binomial/quantal responses.

Usage

W1.2(upper = 1, fixed = c(NA, NA), names = c("b", "e"), ...)
  
  W2.2(upper = 1, fixed = c(NA, NA), names = c("b", "e"), ...)

Arguments

`upper`	numeric value. The fixed, upper limit in the model. Default is 1.
`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.
`...`	additional arguments to be passed from the convenience functions.

Details

The two-parameter Weibull model is given by the expression

f(x) = \exp(-\exp(b(\log(x)-e))).

The function is asymmetric about the inflection point, that is the parameter \exp(e).

Value

See weibull1.

Note

This function is for use with the function drm.

Author(s)

Christian Ritz

Examples

## Fitting a two-parameter Weibull model
earthworms.m1 <- drm(number/total~dose, weights = total,
data = earthworms, fct = W1.2(), type = "binomial")

summary(earthworms.m1)

drc

Analysis of Dose-Response Curves

v3.0-1

GPL-2 | file LICENCE

Authors

Christian Ritz <ritz@bioassay.dk>, Jens C. Strebig <streibig@bioassay.dk>

Initial release

2016-08-25

W2