US Car Price Data

Description

U.S. data extracted from Cars93, a data frame in the MASS package.

Usage

carprice

Format

This data frame contains the following columns:

Type

Type of car, e.g. Sporty, Van, Compact

Min.Price

Price for a basic model

Price

Price for a mid-range model

Max.Price

Price for a `premium' model

Range.Price

Difference between Max.Price and Min.Price

RoughRange

Rough.Range plus some N(0,.0001) noise

gpm100

The number of gallons required to travel 100 miles

MPG.city

Average number of miles per gallon for city driving

MPG.highway

Average number of miles per gallon for highway driving

Source

MASS package

References

Venables, W.N. and Ripley, B.D., 3$^{rd}$ edn 1999. Modern Applied Statistics with S-Plus. Springer, New York.\ See also `R' Complements to Modern Applied Statistics with S-Plus, available from \ http://www.stats.ox.ac.uk/pub/MASS3/.

Examples

 
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 alone