Three-parameter log-logistic function with upper limit fixed — LL.3u • drc

A three-parameter log-logistic function with upper limit fixed (default 1), primarily for use with binomial/quantal dose-response data.

Usage

LL.3u(upper = 1, fixed = c(NA, NA, NA), names = c("b", "c", "e"), ...)

l3u(upper = 1, fixed = c(NA, NA, NA), names = c("b", "c", "e"), ...)

Arguments

upper: numeric value, the fixed upper limit (default 1).
fixed: numeric vector of length 3, specifying fixed parameters (use NA for non-fixed parameters).
names: character vector of length 3, specifying the names of the parameters (default: b, c, e).
...: additional arguments to llogistic.

Value

See llogistic.

Details

The three-parameter log-logistic function with upper limit fixed is given by $$f(x) = c + \frac{upper-c}{1+\exp(b(\log(x)-\log(e)))}$$

See also

LL.2, LL.3, LL.4, llogistic

Author

Christian Ritz