drc (version 1.0-3)

l5: The five-parameter logistic function

Description

'l5' provides the five-parameter logistic function, self starter function and names of the parameters.

Usage

l5(fixed = c(NA, NA, NA, NA, NA), names = c("b", "c", "d", "e", "f"), useDer = FALSE, w = 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!

w

logical. If TRUE weighted regression is applied to determine the start values.

Value

• See logistic.

Details

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

References

Finney, D. J. (1979) Bioassay and the Practise of Statistical Inference, Int. Statist. Rev., 47, 1--12.

See Also

Related functions are l4 and l3.

Examples

model1 <- multdrc(FA, fct=l5())
summary(model1)

rm(model1)