#
# EPage 241
#
# 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(DAAG)

toycars$car = as.factor(toycars$car)

# Part (a):
#
toycars.lm_a = lm( distance ~ angle + car, data=toycars )

# Part (b):
#
plot( toycars.lm_a, which=1 )

# Part (c):
#
toycars.lm_c = lm( distance ~ angle:car, data=toycars ) # we can also use distance ~ angle + angle:car to get this fit ... I don't know which is better / preferred
plot( toycars.lm_c )