#how to use the drc, Install it
install.packages(“drc”, dependencies=TRUE)
and load it
library(drc)
#Execute (data ryegrass are for training in drc)
ryegrass.m0 <- drm(rootl ~ conc, data = ryegrass, fct = LL.4(names=c(“Slope”,”Lower Limit”,”Upper Limit”,”ED50″)))
#Parameter estimates
summary(ryegrass.m0)
Model fitted: Log-logistic (ED50 as parameter) (4 parms)
Parameter estimates:
Estimate Std. Error t-value p-value
Slope:(Intercept) 2.98222 0.46506 6.41251 0.0000
Lower Limit:(Intercept) 0.48141 0.21219 2.26876 0.0345
Upper Limit:(Intercept) 7.79296 0.18857 41.32722 0.0000
ED50:(Intercept) 3.05795 0.18573 16.46440 0.0000
Residual standard error: 0.5196256 (20 degrees of freedom)
#Plot
plot(ryegrass.m0, broken=TRUE, xlab=”Dose (mM)”, ylab=”Root length (cm)”, lwd=2, cex=1.2, cex.axis=1.2, ex.lab=1.2)