Chart Classes

The base class used to display a chart is the IlvChartGraphic class. This class defines a chart object as a graphic object that can be used in the same way as all the other graphic objects defined in Views.

When you create a chart object, an IlvMemoryChartData object (inherited from IlvAbstractChartData) is created by default and is set on the created chart to handle the storage of the data sets it is going to display. You can either use this chart data object created by default or set your own chart data object.

The way the data are projected into screen coordinates is not specified at the level of the IlvChartGraphic class since it depends on the system of coordinates in which the data to be displayed are expressed. No object is defined by default to display the scales since the type depends on the way the data are projected into screen coordinates. Two subclasses of the IlvChartGraphic class are provided. These subclasses predefine the way the data are projected and the objects to be used to display the scales.

• The IlvCartesianChart class is instantiated to represent data in a standard way. The data are expressed in a Cartesian system of coordinates (x, y). Two rectangular scales are created by default: one representing the abscissa values x and one representing the ordinate values y.

• The IlvPolarChart class is instantiated to represent data in a circular way. The data are expressed in a polar system of coordinates (q, r). A circular scale is created by default to represent the abscissa values q. A rectangular scale is created by default to represent the ordinate values r.

By using one of these subclasses instead of the IlvChartGraphic class, you only need to set the following objects when you create a chart:

• The data sets to be displayed with the considered chart.

• The displayers used to draw the graphical representations of the data sets in the considered chart.