#
# Epage 41
#
# Written by:
# -- 
# John L. Weatherwax                2009-04-21
# 
# email: wax@alum.mit.edu
# 
# Please send comments and especially bug reports to the
# above email address.
# 
#-----

library(alr3)
data(wblake)
attach(wblake)

m <- lm( Length ~ Age )

plot(Age,Length)
abline(m)

summary( m )

anova(m)

# 2.5.1: 
#
predict(m,data.frame(Age=c(2,4,6)), interval="confidence", level=0.95)

# 2.5.2: 
#
predict(m,data.frame(Age=c(9)), interval="confidence", level=0.95)

# 2.5.3: 
#
data(wblake2)
attach(wblake2)

postscript("../../WriteUp/Graphics/Chapter2/prob_5_wblake2.eps", onefile=FALSE, horizontal=FALSE)
plot( Age, Length, xlab="Age", ylab="Length" )
abline( m2 ) 
dev.off()

m2 <- lm( Length ~ Age ) 

y_hat <- predict( m2 )
res   <- m2$residuals 

postscript("../../WriteUp/Graphics/Chapter2/prob_5_wblake2_residuals.eps", onefile=FALSE, horizontal=FALSE)
plot( y_hat, res, xlab="Fitted values", ylab="Residuals" )
dev.off()