drc (version 2.5-12)

LL.5: The five-parameter log-logistic function

Description

'LL.5' and 'LL2.5' provide the five-parameter log-logistic function, self starter function and names of the parameters.

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"), ...)
  
  LL2.5(fixed = c(NA, NA, NA, NA, NA), names = c("b", "c", "d", "e", "f"), ...)

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.

...

Additional arguments (see llogistic).

Value

• See llogistic.

concept

Hill 5-parameter five-parameter

Details

The five-parameter logistic function is given by the expression $$f(x) = c + \frac{d-c}{(1+\exp(b(\log(x)-\log(e))))^f}$$ or in another parameterisation $$f(x) = c + \frac{d-c}{(1+\exp(b(\log(x)-e)))^f}$$ 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 LL.4 and LL.3.

Examples

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