public Object clone() throws CloneNotSupportedException {
        CombinedRangeCategoryPlot result 
            = (CombinedRangeCategoryPlot) super.clone(); 
        result.subplots = (List) ObjectUtilities.deepClone(this.subplots);
        for (Iterator it = result.subplots.iterator(); it.hasNext();) {
            Plot child = (Plot) it.next();
            child.setParent(result);
        }
        
        // after setting up all the subplots, the shared range axis may need 
        // reconfiguring
        ValueAxis rangeAxis = result.getRangeAxis();
        if (rangeAxis != null) {
            rangeAxis.configure();
        }
        
        return result;