Girth, Height and Volume for Black Cherry Trees
This data set provides measurements of the girth, height and volume
of timber in 31 felled black cherry trees. Note that girth is the
diameter of the tree (in inches) measured at 4 ft 6 in above the
ground.
Usage
trees
Format
A data frame with 31 observations on 3 variables.
[,1]  Girth  numeric
 Tree diameter in inches 
[,2]  Height  numeric
 Height in ft 
[,3]  Volume  numeric
 Volume of timber in cubic ft 
Source
Ryan, T. A., Joiner, B. L. and Ryan, B. F. (1976)
The Minitab Student Handbook.
Duxbury Press.
References
Atkinson, A. C. (1985)
Plots, Transformations and Regression.
Oxford University Press.
Examples
require(stats); require(graphics)
pairs(trees, panel = panel.smooth, main = "trees data")
plot(Volume ~ Girth, data = trees, log = "xy")
coplot(log(Volume) ~ log(Girth)  Height, data = trees,
panel = panel.smooth)
summary(fm1 < lm(log(Volume) ~ log(Girth), data = trees))
summary(fm2 < update(fm1, ~ . + log(Height), data = trees))
step(fm2)
## i.e., Volume ~= c * Height * Girth^2 seems reasonable
