US Car Price Data
U.S. data extracted from Cars93, a data frame in the
MASS package.
carprice
This data frame contains the following columns:
Type of car, e.g. Sporty, Van, Compact
Price for a basic model
Price for a mid-range model
Price for a ‘premium’ model
Difference between Max.Price and Min.Price
Rough.Range plus some N(0,.0001) noise
The number of gallons required to travel 100 miles
Average number of miles per gallon for city driving
Average number of miles per gallon for highway driving
MASS package
Venables, W.N.\ and Ripley, B.D., 4th edn 2002. Modern Applied Statistics with S. Springer, New York.
See also ‘R’ Complements to Modern Applied Statistics with S-Plus, available from http://www.stats.ox.ac.uk/pub/MASS3/
print("Multicollinearity - Example 6.8")
pairs(carprice[,-c(1,8,9)])
carprice1.lm <- lm(gpm100 ~ Type+Min.Price+Price+Max.Price+Range.Price,
data=carprice)
round(summary(carprice1.lm)$coef,3)
pause()
alias(carprice1.lm)
pause()
carprice2.lm <- lm(gpm100 ~ Type+Min.Price+Price+Max.Price+RoughRange, data=carprice)
round(summary(carprice2.lm)$coef, 2)
pause()
carprice.lm <- lm(gpm100 ~ Type + Price, data = carprice)
round(summary(carprice.lm)$coef,4)
pause()
summary(carprice1.lm)$sigma # residual standard error when fitting all 3 price variables
pause()
summary(carprice.lm)$sigma # residual standard error when only price is used
pause()
vif(lm(gpm100 ~ Price, data=carprice)) # Baseline Price
pause()
vif(carprice1.lm) # includes Min.Price, Price & Max.Price
pause()
vif(carprice2.lm) # includes Min.Price, Price, Max.Price & RoughRange
pause()
vif(carprice.lm) # Price alonePlease choose more modern alternatives, such as Google Chrome or Mozilla Firefox.