function nth(int $nth, int $offset = 0) {
        if($nth <= 0) {
            throw new \InvalidArgumentException('nth must be a non-zero positive integer');
        }
        
        $new = array();
        $size = \count($this->data);
        
        for($i = $offset; $i < $size; $i += $nth) {
            $new[] = $this->data[$i];
        }
        
        return (new self($new));
    }