R: The two-parameter Weibull functions

W1.2 {drc} | R Documentation

## 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

### See Also

Related functions are `W1.3`, `W1.4`, `weibull1` and `weibull2`.

### 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)

[Package drc version 3.0-1 Index]