The five-parameter log-logistic function
'LL.5' and 'LL2.5' provide the five-parameter log-logistic function, self starter function and names of the parameters.
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"), ...)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 |
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.
See llogistic.
This function is for use with the function drm.
Christian Ritz
Finney, D. J. (1979) Bioassay and the Practise of Statistical Inference, Int. Statist. Rev., 47, 1–12.
ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = LL.5()) summary(ryegrass.m1)
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