#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)