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 |

### 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)
```

*drc*version 3.0-1 Index]