public double getStartYValue(int series, int item) {
        YIntervalSeries s = (YIntervalSeries) this.data.get(series);
        return s.getYLowValue(item);
    }

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