#
# EPage 215
#
# 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.
# 
#-----

save_plots = F

#install.packages("MPV")

library(lattice) # needed for xyplot 
library(DAAG)
library(MPV)

set.seed(0)

table.b3$x11 = as.factor( table.b3$x11 )

# Part (a): 
if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/prob_10_y_vs_x1_scatter_plot.eps", onefile=FALSE, horizontal=FALSE) }
plot( y ~ x1, data=table.b3 )
if( save_plots ){ dev.off() }

# Part (b):
xyplot( y ~ x1 | x11, data=table.b3 )

# Part (c):
m0 = lm( y ~ x1 + x11, data=table.b3 )

if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/prob_10_y_vs_x1_N_x11_resid_vs_fitted_plot.eps", onefile=FALSE, horizontal=FALSE) }
plot( m0, which=1 )
if( save_plots ){ dev.off() }

# Lets add a quadradic term and see how well this improves the model ... it actually looks better:
m1 = lm( y ~ x1 + I(x1^2) + x11, data=table.b3 )
plot( m1, which=1 )

# Part (d):
xyplot( m0$residuals ~ x7 | x11, data=table.b3 )