source('../../Data/data_loaders.R')

DF = load_appendix_gas_mileage_data()

# Part (a):
#
m = lm( MPG ~ DISP + HP + WT, data=DF )
print( summary(m) )

# Part (b):
#
print( cor( DF ) )

# Part (c):
#
#postscript("../../WriteUp/Graphics/Chapter4/ex_4_5_pairs_plot.eps", onefile=FALSE, horizontal=FALSE)
pairs( DF )
#dev.off()

#postscript("../../WriteUp/Graphics/Chapter4/ex_4_5_boxplot.eps", onefile=FALSE, horizontal=FALSE)
boxplot( DF )
#dev.off()

# Part (d):
#
#postscript("../../WriteUp/Graphics/Chapter4/ex_4_5_residuals_vs_fitted.eps", onefile=FALSE, horizontal=FALSE)
plot( m, which=1 )
#dev.off()

r = m$residuals

#postscript("../../WriteUp/Graphics/Chapter4/ex_4_5_residuals_vs_features.eps", onefile=FALSE, horizontal=FALSE)
par(mfrow=c(1, 3))
plot( DF$DISP, r, type='p', pch=19, xlab='DISP', ylab='residuals' )
grid()

plot( DF$HP, r, type='p', pch=19, xlab='HP', ylab='residuals' )
grid()

plot( DF$WT, r, type='p', pch=19, xlab='WT', ylab='residuals' )
grid()
par(mfrow=c(1, 1))
#dev.off()

# Part (e):
#
plot( m, which=2 )