LL.5 {drc}

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).

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.

Value

See llogistic.

Note

This function is for use with the function drm.

Author(s)

Christian Ritz

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)