LL.5 {drc} R Documentation

## 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.

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)



[Package drc version 3.0-1 Index]