public function getColumn($index)
    {
        if ($index >= count($this->getRow(0))) {
            throw new NodeException(sprintf('Column #%d does not exist in table.', $index));
        }

        $rows = $this->getRows();
        $column = array();

        foreach ($rows as $row) {
            $column[] = $row[$index];
        }

        return $column;
    }