GroupRenderer is a special implementation of XYSeriesRenderer that combines multiple instances
of XYSeries into a single virtual series of s higher dimension. Examples of GroupRenderer are:
- BarRenderer
- CandlestickRenderer
Let's take a quick look at CandlestickRenderer. A candlestick chart is basically a two two dimensional
representation of a complex value; for every value of x a single candlestick is drawn, but there are
four values (dimensions) that make up each candlestick:
- open
- close
- high
- low
When a series is added to the plot with a formatter associated with a renderer that extends GroupRenderer,
all series added with formatters of the same type are automatically "grouped" together during rendering.