public void area(double value,Paint color,boolean stack){
  SourcedPlotElement parent=stack ? findParent() : null;
  plotElements.add(new ConstantArea(value,color,parent));
}

public void area ( double value , Paint color , boolean stack ) { SourcedPlotElement parent = stack ? findParent ( ) : null ; plotElements . add ( new ConstantArea ( value , color , parent ) ) ; }
add a area like any other but with a constant value , it can be stacked like any other area
