W2 function

The two-parameter Weibull functions

'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.

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

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

Returns

See weibull1.

Author(s)

Christian Ritz

Note

This function is for use with the function drm.

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)