Root length measurements
Data stem from an experiment assessing the inhibitory effect of secalonic acids on plant growth.
data(secalonic)
A data frame with 7 observations on the following 2 variables:
dosea numeric vector containing dose values (mM)
rootla numeric vector containing root lengths (cm)
For each dose the root length is an average three measurements.
Gong, X. and Zeng, R. and Luo, S. and Yong, C. and Zheng, Q. (2004) Two new secalonic acids from Aspergillus Japonicus and their allelopathic effects on higher plants, Proceedings of International Symposium on Allelopathy Research and Application, 27-29 April, Shanshui, Guangdong, China (Editors: R. Zeng and S. Luo), 209–217.
Ritz, C (2009) Towards a unified approach to dose-response modeling in ecotoxicology To appear in Environ Toxicol Chem.
## Fitting a four-parameter log-logistic model secalonic.m1 <- drm(rootl ~ dose, data = secalonic, fct = LL.4()) summary(secalonic.m1) ## Fitting a three-parameter log-logistic model ## lower limit fixed at 0 secalonic.m2 <- drm(rootl ~ dose, data = secalonic, fct = LL.3()) summary(secalonic.m1) ## Comparing logistic and log-logistic models ## (Figure 1 in Ritz (2009)) secalonic.LL4 <- drm(rootl ~ dose, data = secalonic, fct = LL.4()) secalonic.L4 <- drm(rootl ~ dose, data = secalonic, fct = L.4()) plot(secalonic.LL4, broken=TRUE, ylim=c(0,7), xlab="Dose (mM)", ylab="Root length (cm)", cex=1.2, cex.axis=1.2, cex.lab=1.2, lwd=2) plot(secalonic.L4, broken=TRUE, ylim=c(0,7), add=TRUE, type="none", lty=2, lwd=2) abline(h=coef(secalonic.L4)[3], lty=3, lwd=2)
Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.