public Number getMedianValue(int row, int column) {
        Number result = null;
        BoxAndWhiskerItem item = (BoxAndWhiskerItem) this.data.getObject(row, 
                column);
        if (item != null) {
            result = item.getMedian();
        }
        return result;
    }

    /**
     * Returns the median value for an item.
     *
     * @param rowKey  the row key.
     * @param columnKey  the columnKey.
     *
     * @return The median value.
     * 
     * @see #getItem(int, int)
     */
    public Number getMedianValue(Comparable rowKey, Comparable columnKey) {
        Number result = null;
        BoxAndWhiskerItem item = (BoxAndWhiskerItem) this.data.getObject(
                rowKey, columnKey);
        if (item != null) {
            result = item.getMedian();
        }
        return result;