R: Potency of two herbicides

S.alba {drc} | R Documentation

## Potency of two herbicides

### Description

Data are from an experiment, comparing the potency of the two herbicides glyphosate and bentazone in white mustard Sinapis alba.

### Usage

    data(S.alba)

### Format

A data frame with 68 observations on the following 3 variables.

`Dose`

  a numeric vector containing the dose in g/ha.

`Herbicide`

  a factor with levels `Bentazone` `Glyphosate` (the two herbicides applied).

`DryMatter`

  a numeric vector containing the response (dry matter in g/pot).

### Details

The lower and upper limits for the two herbicides can be assumed identical, whereas slopes and ED50 values are different (in the log-logistic model).

### Source

Christensen, M. G. and Teicher, H. B., and Streibig, J. C. (2003) Linking fluorescence induction curve and biomass in herbicide screening, Pest Management Science, 59, 1303–1310.

### See Also

See the examples sections for `drm` and `EDcomp`.

### Examples

    ## Fitting a log-logistic model with
    ##  common lower and upper limits
    S.alba.LL.4.1 <- drm(DryMatter~Dose, Herbicide, data=S.alba, fct = LL.4(),
    pmodels=data.frame(Herbicide,1,1,Herbicide))
    summary(S.alba.LL.4.1)

    ## Applying the optimal transform-both-sides Box-Cox transformation
    ## (using the initial model fit)
    S.alba.LL.4.2 <- boxcox(S.alba.LL.4.1, method = "anova")
    summary(S.alba.LL.4.2)

    ## Plotting fitted regression curves together with the data
    plot(S.alba.LL.4.2)

[Package drc version 3.0-1 Index]