trees {datasets}R Documentation

Diameter, Height and Volume for Black Cherry Trees

Description

This data set provides measurements of the diameter, height and volume of timber in 31 felled black cherry trees. Note that the diameter (in inches) is erroneously labelled Girth in the data. It is 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 (rather than girth, actually) 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
[Package datasets version 3.6.0 Index]