#
# 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(datasets)

#postscript("../../WriteUp/Graphics/Chapter5/prob_3_plot.eps", onefile=FALSE, horizontal=FALSE)

plot( dist ~ speed, data=cars, ylab="distance" )

m1 = lm( dist ~ speed, data=cars )
abline( m1 )

m2 = lm( dist ~ speed + I(speed^2), data=cars )
lines( cars$speed, fitted(m2), col="blue" )

#dev.off()

summary(m2)
anova(m1,m2)

#plot( diff(dist) ~ speed[1:(length(speed)-1)], data=cars )