public double getCloseValue(int series, int item) {
        double result = Double.NaN;
        Number close = getClose(series, item);
        if (close != null) {
            result = close.doubleValue();
        }
        return result;
    }

    /**
     * Returns the trading volume.
     *
     * @param series  the series index (ignored).
     * @param item  the item index (zero-based).
     *
     * @return The trading volume.
     */
    public Number getVolume(int series, int item) {
        return this.data[item].getVolume();
    }

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

    /**
     * Returns the series count.
     *
     * @return 1.
     */
    public int getSeriesCount() {
        return 1;
    }

    /**
     * Returns the item count for the specified series.
     *
     * @param series  the series index (ignored).
     *
     * @return The item count.
     */
    public int getItemCount(int series) {
        return this.data.length;