## Measurements on a Selection of Books

### Description

The `allbacks`

data frame gives measurements
on the volume and weight of 15 books, some of which
are softback (pb) and some of which are hardback (hb). Area
of the hardback covers is also included.

### Usage

allbacks

### Format

This data frame contains the following columns:

- volume
book volumes
in cubic centimeters

- area
hard board cover
areas in square centimeters

- weight
book weights in grams

- cover
a factor with levels
`hb`

hardback, `pb`

paperback

### Source

The bookshelf of J. H. Maindonald.

### Examples

print("Multiple Regression - Example 6.1")
attach(allbacks)
volume.split <- split(volume, cover)
weight.split <- split(weight, cover)
plot(weight.split$hb ~ volume.split$hb, pch=16, xlim=range(volume), ylim=range(weight),
ylab="Weight (g)", xlab="Volume (cc)")
points(weight.split$pb ~ volume.split$pb, pch=16, col=2)
pause()
allbacks.lm <- lm(weight ~ volume+area)
summary(allbacks.lm)
detach(allbacks)
pause()
anova(allbacks.lm)
pause()
model.matrix(allbacks.lm)
pause()
print("Example 6.1.1")
allbacks.lm0 <- lm(weight ~ -1+volume+area, data=allbacks)
summary(allbacks.lm0)
pause()
print("Example 6.1.2")
oldpar <- par(mfrow=c(2,2))
plot(allbacks.lm0)
par(oldpar)
allbacks.lm13 <- lm(weight ~ -1+volume+area, data=allbacks[-13,])
summary(allbacks.lm13)
pause()
print("Example 6.1.3")
round(coef(allbacks.lm0),2) # Baseline for changes
round(lm.influence(allbacks.lm0)$coef,2)