trees                package:datasets                R Documentation

Girth, Height and Volume for Black Cherry Trees

Description:

     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

