# 
# 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.
# 
#-----

#
# EPage 139
#

save_plots = F

DF = read.csv( "../../Data/gasoline.csv", header=TRUE )
rownames(DF) = DF$country
DF$country = NULL

DF$sqrtCons = sqrt(DF$consumption)

m_direct = lm( price ~ consumption, data=DF )
s_direct = summary(m_direct)
influe_direct = influence(m_direct)

if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/ex_4_direct.eps", onefile=FALSE, horizontal=FALSE) }
plot( DF$consumption, DF$price )
abline(m_direct)
grid()
if( save_plots ){ dev.off() }

m_sqrt = lm( price ~ sqrtCons, data=DF )
s_sqrt = summary(m_sqrt)
influe_sqrt = influence(m_sqrt)

if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/ex_4_sqrt.eps", onefile=FALSE, horizontal=FALSE) }
plot( sqrt(DF$consumption), DF$price )
abline(m_sqrt)
grid()
if( save_plots ){ dev.off() }

m_log = lm( price ~ I(log(consumption)), data=DF )
s_log = summary(m_log)
influe_log = influence(m_log)

if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/ex_4_log.eps", onefile=FALSE, horizontal=FALSE) }
plot( log(DF$consumption), DF$price )
abline(m_log)
grid()
if( save_plots ){ dev.off() }

# What city has the most influence:
all_influence = rbind( influe_direct$hat, influe_sqrt$hat, influe_log$hat )
if( save_plots ){ postscript("../../WriteUp/Graphics/Chapter6/ex_4_boxplot.eps", onefile=FALSE, horizontal=FALSE) }
boxplot( all_influence )
if( save_plots ){ dev.off() }

all_influence['Singapore']