H.virescens {drc} | R Documentation |
For three days, moths of the tobacco budworm (Heliothis virescens) were exposed to doses of the pyrethroid trans-cypermethrin.
data(H.virescens)
A data frame with 12 observations on the following 4 variables.
dose
numdead
total
sex
F
M
denoting a grouping according to sexIn Venables and Ripley (2002), these data are analysed using a logistic regression with base-2 logarithm of dose as explanatory variable.
Venables, W. N. and Ripley, B. D (2002) Modern Applied Statistics with S, New York: Springer (fourth edition).
## Fitting dose-response model (log-logistic with common slope) Hv.m1 <- drm(numdead/total~dose, sex, weights = total, data = H.virescens, fct = LL.2(), pmodels = list(~1,~sex), type = "binomial") summary(Hv.m1) ## Fitting the same model as in Venables and Riply (2002) Hv.m2 <- glm(cbind(numdead, total-numdead)~sex+I(log2(dose))-1, data = H.virescens, family = binomial) ## Comapring the fits logLik(Hv.m1) logLik(Hv.m2) ## Estimated ED values (matching those given in MASS) ED(Hv.m1, c(25, 50, 75))