A Graph object is defined as a container for geometric objects which also contains the type of information common to all graphs (for example, titles, axis labels and scales, and the like). A Graph object can be asked to plot itself; the user can supply one or more Plotter objects to the Graph, or else leave it up to the Graph to try to obtain its own default Plotter object. The base class Graph is not normally instantiated as is. Instead, the user will normally instantiate its derived classes, Graph2d and Graph3d.