public TableOrder getDataExtractOrder() {
        return this.dataExtractOrder;
    }

    /**
     * Sets the data extract order (by row or by column) and sends a
     * {@link PlotChangeEvent}to all registered listeners.
     *
     * @param order the order (<code>null</code> not permitted).
     *
     * @throws IllegalArgumentException if <code>order</code> is
     *     <code>null</code>.
     *
     * @see #getDataExtractOrder()
     */
    public void setDataExtractOrder(TableOrder order) {
        if (order == null) {
            throw new IllegalArgumentException("Null 'order' argument");
        }
        this.dataExtractOrder = order;
        fireChangeEvent();
    }

    /**
     * Returns the head percent.
     *
     * @return The head percent.
     *
     * @see #setHeadPercent(double)
     */
    public double getHeadPercent() {
        return this.headPercent;