BC.3.fun | R Documentation |
These functions provide the Brain-Cousens models for describing u-shaped hormesis. They can be used with 'nls()' or 'nlme()' or 'gnls()' and they do not contain self-starting routines.
BC.5.fun(predictor, b, c, d, e, f)
BC.4.fun(predictor, b, d, e, f)
BC.3.fun(predictor, b, e, f)
predictor |
a numeric vector of values at which to evaluate the model |
b |
model parameter: slope near to the inflection point |
c |
model parameter: lower asymptote |
d |
model parameter: higher asymptote |
e |
model parameter: dose at inflection point |
f |
model parameter for hormesis |
The model functions for the Brain-Cousens model (Brain and Cousens, 1989) is
f(x, b,c,d,e,f) = c + \frac{d-c+fx}{1+\exp(b(\log(x)-\log(e)))}
,
f(x, b,d,e,f) = c + \frac{d+fx}{1+\exp(b(\log(x)-\log(e)))}
,
f(x, b,e,f) = c + \frac{1+fx}{1+\exp(b(\log(x)-\log(e)))}
, These functions do not provide a selfStarting routine, but you can obtain starting values from a drc fit, by using the corresponding functions BC.4() and BC.5().
These functions return a numeric value
Andrea Onofri
Ratkowsky, DA (1990) Handbook of nonlinear regression models. New York (USA): Marcel Dekker Inc. Onofri, A. (2020). A collection of self-starters for nonlinear regression in R. See: https://www.statforbiology.com/2020/stat_nls_usefulfunctions/ 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.
X <- c(1, 3, 5, 7, 9, 11, 13, 20)
Y <- c(8.22, 14.0, 17.2, 16.9, 19.2, 19.6, 19.4, 19.6)
# nls fit
model <- nls(Y ~ NLS.asymReg(X, init, m, plateau) )
# drm fit
model <- drm(Y ~ X, fct = DRC.asymReg())
summary(model)
model2 <- drm(Y ~ X, fct = DRC.SSasymp())
summary(model2)
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