drc (version 1.2-0)

acidiq: Acifluorfen and diquat tested on Lemna minor.

Description

Data from an experiment where the chemicals acifluorfen and diquat tested on Lemna minor. The dataset has 7 mixtures used in 8 dilutions with three replicates and 12 common controls, in total 180 observations.

Usage

data(acidiq)

source

The dataset is kindly provided by Nina Cedergreen, Department of Agricultural Sciences, Royal Veterinary and Agricultural University, Denmark.

Details

The dataset is analysed in S{\o}rensen et al (2006). Hewlett's symmetric model seems appropriate for this dataset.

References

S{\o}rensen, H. and Cedergreen, N. and Skovgaard, I. M. and Streibig, J. C. (2006) An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments, Statistical Ecology and Environmental Statistics, 13. ?--??.

Examples

## Fitting the model with freely varying ED50 values
model1 <- multdrc(rgr1~dose1, pct1, data=acidiq, 
collapse=list(~factor(pct1),~1,~1,~factor(pct1) - 1), 
boxcox=TRUE)
summary(model1)


## Fitting the concentration addition model
model1ca <- mixture(rgr1~dose1, pct1, data=acidiq, collapse=~factor(pct1), 
model="CA", boxcox=TRUE)
anova(model1ca)  # comparison to model with freely varying e parameter
summary(model1ca)


## Fitting the Hewlett model
model1h <- mixture(rgr1~dose1, pct1, data=acidiq, collapse=~factor(pct1), 
model="Hewlett", boxcox=TRUE)
anova(model1h)  # comparison to a model with freely varying e parameter
anova(model1ca, model1h)  # rejecting concentration addition
summary(model1h)


## Fitting the Voelund model
model1v <- mixture(rgr1~dose1, pct1, data=acidiq, collapse=~factor(pct1), 
model="Voelund", boxcox=TRUE)
anova(model1v)  # comparison to a model with freely varying e parameter
summary(model1v)


rm(model1, model1ca, model1h, model1v)