ryegrass.RdA single dose-response curve.
data(ryegrass)
A data frame with 24 observations on the following 2 variables.
a numeric vector of root lengths
a numeric vector of concentrations of ferulic acid
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.
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.
# NOT RUN { library(drc) ## 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) # }