drc (version 0.8-2)

l3: The three-parameter logistic function (lower limit equal to zero)

Description

'l3' provides the three-parameter logistic function, self starter function and names of the parameters.

Usage

l3(fixed = c(NA, NA, NA), names = c("b", "d", "e"), useDer = FALSE)

Arguments

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.

useDer

logical. If TRUE derivatives are supplied, otherwise they are not supplied. Not implemented!

Value

• See logistic.

Details

The three-parameter logistic function is given by the expression $$f(x) = 0 + \frac{d-0}{1+\exp(b(\log(x)-\log(e)))}$$ The function is symmetric about the inflection point ($e$).

See Also

A related function is l4 and the more general logistic.

Examples

model1 <- multdrc(FA, fct=l3())
model1

rm(model1)