Five-parameter log-logistic function

A five-parameter (generalized) log-logistic function. The function is asymmetric when f differs from 1.

Usage

LL.5(fixed = c(NA, NA, NA, NA, NA), names = c("b", "c", "d", "e", "f"), ...)

l5(fixed = c(NA, NA, NA, NA, NA), names = c("b", "c", "d", "e", "f"), ...)

Arguments

fixed: numeric vector of length 5, specifying fixed parameters (use NA for non-fixed parameters).
names: character vector of length 5, specifying the names of the parameters (default: b, c, d, e, f).
...: additional arguments to llogistic.

Value

See llogistic.

Details

The five-parameter log-logistic function is given by the expression $$f(x) = c + \frac{d-c}{(1+\exp(b(\log(x)-\log(e))))^f}$$

Author

Christian Ritz

Examples

ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = LL.5())