pdf("ex0108.pdf")

# Read in data from ASCII formatted (Fixed With File)

ex0108dat <- read.fwf("http://www.stat.ufl.edu/~winner/data/biostat/ex0108.dat", width=c(8,8,8,7), 
        col.names=c("subject","drugid","theophclrnc","drugname"))


# Create a dataset (frame) from input data

ex0108 <- data.frame(ex0108dat)

# Attach the dataset for analysis 

attach(ex0108)

# Plot Theophylline Clearance versus Interacting Drug (joining points by subject)

interaction.plot(drugname, subject, theophclrnc)

# Plot Theophylline Clearance versus Subject (joning points by drug)

interaction.plot(subject, drugname, theophclrnc)


dev.off()