daphnids {drc} | R Documentation |
The number of immobile daphnids –in contrast to mobile daphnids– out of a total of 20 daphnids was counted for several concentrations of a toxic substance.
data(daphnids)
A data frame with 16 observations on the following 4 variables.
dose
no
total
time
24h
48h
The same daphnids were counted at 24h and later again at 48h.
Nina Cedergreen, Faculty of Life Sciences, University of Copenhagen, Denmark.
## Fitting a model with different parameters ## for different curves ## using 'multdrc' daphnids.m1 <- multdrc(no/total~dose, time, weights=total, data=daphnids, fct=l2(), type="binomial") summary(daphnids.m1) ## Goodness-of-fit test anova(daphnids.m1) ## Fitting a model with a common intercept parameter ## using 'multdrc' daphnids.m2 <- multdrc(no/total~dose, time, weights=total, data=daphnids, fct=l2(), type="binomial", collapse=list(~1, ~time)) ## The same fits using 'drm' daphnids.m1 <- drm(no/total~dose, time, weights=total, data=daphnids, fct=LL.2(), type="binomial") daphnids.m2 <- drm(no/total~dose, time, weights=total, data=daphnids, fct=LL.2(), type="binomial", pmodels=list(~1, ~time))