public function getVisitorsAndPageViewsForPeriod($startDate, $endDate, $groupBy = 'date')
    {
        $visitorData = [];
        $answer = $this->performQuery($startDate, $endDate, 'ga:visits,ga:pageviews', ['dimensions' => 'ga:'.$groupBy]);

        foreach ($answer->rows as $dateRow) {
            $visitorData[] = [$groupBy => Carbon::createFromFormat(($groupBy == 'yearMonth' ? 'Ym' : 'Ymd'), $dateRow[0]), 'visitors' => $dateRow[1], 'pageViews' => $dateRow[2]];
        }

        return new Collection($visitorData);
    }