CRS.6
is the extension of link{cedergreen}
with freely varying alpha parameter.
For u-shaped hormesis data 'ucedergreen' provides a very general way of specifying the
Cedergreen-Ritz-Streibig modified log-logistic model, under various constraints on the parameters.cedergreen(lowerc = c(-Inf, -Inf, -Inf, -Inf, -Inf),
upperc = c(Inf, Inf, Inf, Inf, Inf), fixed = c(NA, NA, NA, NA, NA),
names = c("b", "c", "d", "e", "f"), alpha, scaleDose = TRUE)
CRS.6(lowerc=c(-Inf, -Inf, -Inf, -Inf, -Inf, -Inf),
upperc=c(Inf, Inf, Inf, Inf, Inf, Inf),
fixed=c(NA, NA, NA, NA, NA, NA),
names=c("b","c","d","e","f","g"))
ucedergreen(lowerc = c(-Inf, -Inf, -Inf, -Inf, -Inf),
upperc = c(Inf, Inf, Inf, Inf, Inf), fixed = c(NA, NA, NA, NA, NA),
names = c("b", "c", "d", "e", "f"), alpha, scaleDose = TRUE)
CRS.4a
, CRS.4a
,
UCRS.5a
and UCRS.5a
where a,b and c coresspond to
the pre-specified alpha values 1, 0.5 and 0.25, respectively.## Modified logistic model with the constraint f>0
lettuce.m1 <- multdrc(weight~conc,data=lettuce,
fct=cedergreen(fixed=c(NA, NA, NA, NA, NA),
lowerc=c(-Inf, -Inf, -Inf, -Inf, 0), alpha=1),
control=mdControl(constr=TRUE))
summary(lettuce.m1)
ED(lettuce.m1, c(10, 50, 90))
## Estimating alpha
lettuce.m2<-drm(weight~conc,data=lettuce,fct=CRS.6())
summary(lettuce.m2)
plot(lettuce.m2) # oops: not increasing until hormesis peak
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