Bug 210635 Incorrect preview of chart after reverse categories.
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/computation/withaxes/PlotWith2DAxes.java
{
		if ( seOrthogonal == null
				|| seOrthogonal.getClass( ) == SeriesImpl.class )
		{
			
			return null;
		}
		OneAxis oaxOrthogonal = findOrthogonalAxis( seOrthogonal );
		if ( oaxOrthogonal == null )
		{
			throw new ChartException( ChartEnginePlugin.ID,
					ChartException.NOT_FOUND,
					"exception.axis.series.link.broken", 
					new Object[]{
						seOrthogonal
					},
					Messages.getResourceBundle( rtc.getULocale( ) ) );
		}
		final OneAxis oaxBase = aax.getPrimaryBase( );
		final SeriesDefinition sdBase = (SeriesDefinition) oaxBase.getModelAxis( )
				.getSeriesDefinitions( )
				.get( 0 );
		final AutoScale scBase = oaxBase.getScale( );
		final AutoScale scOrthogonal = oaxOrthogonal.getScale( );
		final int iTickCount = scBase.getTickCount( );
		int iUnitCount = iTickCount;
		final int iDirection = scBase.getDirection( );
		
		final double dUnitSize = ( iDirection == BACKWARD || ( iDirection == AUTO && aax.areAxesSwapped( ) ) ) ? -scBase.getUnitSize( )
				: scBase.getUnitSize( );