bcl3 {drc} | R Documentation |
'bcl3' provides the four-parameter function, self starter function and names of the parameters.
bcl3(names = c("b", "d", "e", "f"), useDer = FALSE)
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 Brain-Cousens model is given by the expression
f(x) = 0 + frac{d-0+fx}{1+exp(b(log(x)-log(e)))}
which is a four-parameter model.
It is a modification of the three-parameter logistic curve to take hormesis into account.
See braincousens
.
This function is for use with the function multdrc
.
Christian Ritz
van Ewijk, P. H. and Hoekstra, J. A. (1993) Calculation of the EC50 and its Confidence Interval When Subtoxic Stimulus Is Present, ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY, 25, 25–32.
model1 <- multdrc(hormesis[,c(2,1)], fct=bcl3()) summary(model1) ED(model1, c(50)) # compare the parameter estimate and # its estimated standard error # to the values in the above paper rm(model1)