public function breakGroup($key,$func)
    {
        $data = array();
        $start = 0;
        foreach ($this->rows as $i=>$row) {
            if (!isset($oldValue)) {
                $oldValue = $row[$key];
            }

            if ($row[$key]==$oldValue) {
                $oldValue = $row[$key];
                array_push($data, $row);
            } else {
                $func(new DataStore($data, $this->metaData), $start);
                $start = $i;
                $data = array($row);
                $oldValue = $row[$key];
            }
        }
        $func(new DataStore($data, $this->metaData), $start);
    }