public Range getDataRange(ValueAxis axis) {
        Range result = null;
        if (this.subplots != null) {
            Iterator iterator = this.subplots.iterator();
            while (iterator.hasNext()) {
                XYPlot subplot = (XYPlot) iterator.next();
                result = Range.combine(result, subplot.getDataRange(axis));
            }
        }
        return result;