Five-Parameter Log-Logistic Model with log(ED50) as Parameter

A five-parameter log-logistic model where the ED50 is parameterised on the log scale. The mean function is: $$f(x) = c + \frac{d - c}{(1 + \exp(b(\log(x) - e)))^f}$$ where e is the logarithm of the ED50 (not exponentiated).

Usage

llogistic2(
  fixed = c(NA, NA, NA, NA, NA),
  names = c("b", "c", "d", "e", "f"),
  ss = c("1", "2", "3"),
  ssfct = NULL,
  fctName,
  fctText
)

Arguments

fixed

numeric vector of length 5. Specifies which parameters are fixed and at what value. Use NA for parameters that should be estimated.

names

character vector of length 5 giving the names of the parameters b, c, d, e, and f.

ss

character string indicating the self-starter version to use. One of "1" (default), "2", or "3".

ssfct

optional self-starter function. If provided, overrides the built-in self-starter selected by ss.

fctName

optional character string specifying the name of the function.

fctText

optional character string providing a short description of the function.

Value

A list of class "llogistic" containing the nonlinear function, self-starter function, parameter names, and related helper functions.

See also

llogistic, LL2.2, LL2.3, LL2.4, LL2.5

Author

Christian Ritz