| l2 {drc} | R Documentation |
'l2' provides the two-parameter logistic function where the lower limit is fixed at 0 and the upper limit is fixed at 1, mostly suitable for binomial/quantal responses.
l2(fixed = c(NA, NA), names = c("b", "e"), useDer = FALSE)
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. |
useDer |
logical. If TRUE derivatives are supplied, otherwise they are not supplied. Not implemented! |
The two-parameter logistic function is given by the expression
f(x) = frac{1}{1+exp(b(log(x)-log(e)))}
The function is symmetric about the inflection point (e).
See logistic.
This function is for use with the function multdrc.
Christian Ritz
Related functions are l3, l4, l5 and the more general
logistic.
## Fitting a two-parameter logistic model ## to binomial responses (a logit model) model1 <- multdrc(number/total~dose, weights=total, data=earthworms, fct = l2(), type = "binomial") plot(model1) # not fitting at the upper limit! rm(model1)