R: Effect of ferulic acid on growth of ryegrass

ryegrass {drc} | R Documentation

## Effect of ferulic acid on growth of ryegrass

### Description

A single dose-response curve.

### Usage

    data(ryegrass)

### Format

A data frame with 24 observations on the following 2 variables.

rootl

  a numeric vector of root lengths

conc

  a numeric vector of concentrations of ferulic acid

### Details

The data are part of a study to investigate the joint action of phenolic acids on root growth inhibition of perennial ryegrass (Lolium perenne L).

`conc` is the concentration of ferulic acid is in mM, and `rootl` is the root length of perennial ryegrass measured in cm.

### Source

Inderjit and J. C. Streibig, and M. Olofsdotter (2002) Joint action of phenolic acid mixtures and its significance in allelopathy research, Physiologia Plantarum, 114, 422–428, 2002.

### Examples

    ## Displaying the data set
    ryegrass

    ## Fitting a four-parameter Weibull model (type 2)
    ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = W2.4())

    ## Displaying a summary of the model fit
    summary(ryegrass.m1)

    ## Plotting the fitted curve together with the original data
    plot(ryegrass.m1)

    ## Fitting a four-parameter Weibull model (type 1)
    ryegrass.m2 <- drm(rootl ~ conc, data = ryegrass, fct = W1.4())
    plot(ryegrass.m2)

    ## Fitting a four-parameter log-logistic model
    ## with user-defined parameter names
    ryegrass.m3 <- drm(rootl ~ conc, data = ryegrass,
    fct = LL.4(names = c("Slope", "Lower Limit", "Upper Limit", "ED50")))
    summary(ryegrass.m3)

    ## Comparing log-logistic and Weibull models
    ## (Figure 2 in Ritz (2009))
    ryegrass.m0 <- drm(rootl ~ conc, data = ryegrass, fct = LL.4())
    ryegrass.m1 <- drm(rootl ~ conc, data = ryegrass, fct = W1.4())
    ryegrass.m2 <- drm(rootl ~ conc, data = ryegrass, fct = W2.4())

    plot(ryegrass.m0, broken=TRUE, xlab="Dose (mM)", ylab="Root length (cm)", lwd=2,
    cex=1.2, cex.axis=1.2, cex.lab=1.2)
    plot(ryegrass.m1, add=TRUE, broken=TRUE, lty=2, lwd=2)
    plot(ryegrass.m2, add=TRUE, broken=TRUE, lty=3, lwd=2)

    arrows(3, 7.5, 1.4, 7.5, 0.15, lwd=2)
    text(3,7.5, "Weibull-2", pos=4, cex=1.2)

    arrows(2.5, 0.9, 5.7, 0.9, 0.15, lwd=2)
    text(3,0.9, "Weibull-1", pos=2, cex=1.2)

[Package drc version 3.0-1 Index]