drc (version 0.8-2)

bcl4: The four-parameter logistic function with Brain-Cousens' modification

Description

'bcl4' provides the five-parameter function, self starter function and names of the parameters.

Usage

bcl4(names = c("b", "c", "d", "e", "f"), useDer = FALSE)

Arguments

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!

Value

• See braincousens.

Details

The Brain-Cousens model is given by the expression $$f(x) = c + \frac{d-c+fx}{1+\exp(b(\log(x)-\log(e)))}$$ which is a five-parameter model. It is a modification of the four-parameter logistic curve to take hormesis into account.

References

Brain, P. and Cousens, R. (1989) An equation to describe dose responses where there is stimulation of growth at low doses, Weed Research, 29, 93--96.

See Also

The related function bcl3.

Examples

model1 <- multdrc(hormesis[,c(2,1)], fct=bcl4())
anova(model1)
plot(model1)

rm(model1)