Hierarchically grouped boxplot

A modification to boxplot that shows the hierarchical relationships between the grouping variables.

HIERARCHICALBOXPLOT(X,GRP) creates a boxplot of the data in X, grouped according to the grouping variables represented by the columns of GRP. The groupings are shown hierarchically, with the groups in each column of GRP being shown as groups within the groups of the next column.
Known limitation: BOXPLOT readjusts the label positions whenever the figure is resized (including docking/undocking). HIERARCHICALBOXPLOT does *not*. Too much resizing may cause strange-looking label positions.