3.6. Ternary plots are used for compositional data (Aitchison, 1986) where there are three components whose proportions add to one. These are represented by a point in an equilateral triangle, where the distances to the sides add to a constant.

Write an S function to plot a matrix of compositions on a temary diagram.

Apply this to the dataset Skye on the composition of rocks on the Isle of Skye in Scotland. (Our solution can be found on the help page for this dataset, and S-PLUS 2000 has a GUI-graphics example in its sampIes directory.)

xercise habits of students? The pie function takes an argument names which can be used to put labels on each pie slice. Redraw the pie chart with labels. Alternatively, you could add a legend to identify the slices.