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.
Atkinson, A. C. (1985) Plots, Transformations and Regression. Oxford University Press.
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
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