# Hamster Example
# Predict the lifetime of a hamster from its 
# percent of life hibernating. Create the scatterplot, 
# the residual plot, and normal plot of residuals. 

hamster = read.table("c:/datasets/hamster.txt", header=TRUE)

cat("Hamster Dataset:\n")
print(hamster)

cat("Simple Regression Model:\n")
model = lm(hamster$Lifetime ~ hamster$Hiber)
summary(model)

# Send graphics output to PDF file.
pdf("c:/datasets/hamster.pdf")

# Create scatter plot with regression line.
plot(hamster$Hiber, hamster$Lifetime,
   main="Hamster Example Scatterplot",
   xlab="Percent of Life Hibernated",
   ylab="Lifetime in Days")
abline(model, col="red", lty="dashed")

# Create residual plot.
resid = resid(model)
predict = predict(model)
plot(predict, resid,
   main="Hamster Example Residual Plot",
   xlab="Predicted Values",
   ylab="Residuals")
abline(h = 0, col="red", lty="dashed")

# Create normal plot of residuals.
qqnorm(resid,
   main="Hamster Example Normal Plot")
qqline(resid)

# Send graphics output back to screen.
dev.off( )