private function getOverviewsOfSegment($segmentId)
    {
        // get specified segment
        $segmentRepository = $this->em->getRepository('KunstmaanDashboardBundle:AnalyticsSegment');
        $segment = $segmentRepository->find($segmentId);

        if (!$segment) {
            throw new \Exception('Unkown segment ID');
        }

        // get the overviews
        return $segment->getOverviews();
    }