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)