public Number getOpen(int series, int item) {
        return ((OHLCDataset) this.parent).getOpen(this.map[series], item);
    }

    /**
     * Returns the open-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 open-value.
     */
    public double getOpenValue(int series, int item) {
        double result = Double.NaN;
        Number open = getOpen(series, item);
        if (open != null) {
            result = open.doubleValue();   
        }
        return result;