## Glyphosate and metsulfuron-methyl tested on algae.

### Description

The dataset has 7 mixtures, 8 dilutions, two replicates and 5 common control controls.
Four observations are missing, giving a total of 113 observations.

### Usage

data(glymet)

### Format

A data frame with 113 observations on the following 3 variables.

`dose`

a numeric vector of dose values

`pct`

a numeric vector denoting the grouping according to the mixtures percentages

`rgr`

a numeric vector of response values (relative growth rates)

### Details

The dataset is analysed in Soerensen et al (2007).
The concentration addition model can be entertained for this dataset.

### Source

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

### References

Soerensen, H. and Cedergreen, N. and Skovgaard, I. M. and Streibig, J. C. (2007)
An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments,
*Environmental and Ecological Statistics*, **14**, 383–397.

### Examples

## Fitting the model with freely varying ED50 values
glymet.free <- drm(rgr~dose, pct, data = glymet,
fct = LL.3(), pmodels = list(~factor(pct) , ~1, ~factor(pct)))
## Lack-of-fit test
modelFit(glymet.free) # acceptable
summary(glymet.free)
## Plotting isobole structure
isobole(glymet.free, exchange=0.01)
## Fitting the concentration addition model
glymet.ca <- mixture(glymet.free, model = "CA")
## Comparing to model with freely varying e parameter
anova(glymet.ca, glymet.free) # borderline accepted
## Plotting isobole based on concentration addition
isobole(glymet.free, glymet.ca, exchange = 0.01) # acceptable fit
## Fitting the Hewlett model
glymet.hew <- mixture(glymet.free, model = "Hewlett")
### Comparing to model with freely varying e parameter
anova(glymet.ca, glymet.hew)
# borderline accepted
# the Hewlett model offers no improvement over concentration addition
## Plotting isobole based on the Hewlett model
isobole(glymet.free, glymet.hew, exchange = 0.01)
# no improvement over concentration addition