public double getStartXValue(int series, int item) {
        XYIntervalSeries s = (XYIntervalSeries) this.data.get(series);
        return s.getXLowValue(item);
    }

    /**
     * Returns the end x-value (as a double primitive) for an item within a
     * series.
     *
     * @param series  the series index (zero-based).
     * @param item  the item index (zero-based).
     *
     * @return The value.
     */
    public double getEndXValue(int series, int item) {
        XYIntervalSeries s = (XYIntervalSeries) this.data.get(series);
        return s.getXHighValue(item);
    }

    /**
     * Returns the y-value (as a double primitive) for an item within a
     * series.
     *
     * @param series  the series index (zero-based).
     * @param item  the item index (zero-based).
     *
     * @return The value.
     */
    public double getYValue(int series, int item) {
        XYIntervalSeries s = (XYIntervalSeries) this.data.get(series);
        return s.getYValue(item);