public static function _getReportChart($report, $start_date, $end_date, $frequency, $decorator = null)
 {
     $line_chart = new LineChart();
     $line_chart->setTitle($report->getTitle());
     $series = new Series();
     $temp = ReportPeer::getQueryResults($report->getId(), $start_date, $end_date, $frequency);
     if (self::isEmpty($temp)) {
         return null;
     }
     $titles = $report->getQueryTitles();
     $arrays = ReportPeer::fillWithEmptyValues($temp, $start_date, $end_date, $frequency);
     for ($i = 0; $i < sizeof($arrays); $i++) {
         $series->addSerie(new Serie(array_values($arrays[$i]), $titles[$i]));
     }
     $factors = Utils::find_factors(sizeof($arrays[0]) - 1, 7);
     $factor = $factors[sizeof($factors) - 1];
     $labels = array();
     for ($j = 0; $j < $factor + 1; $j++) {
         $labels[] = $j + 1;
     }
     $temp = array_keys($arrays[0]);
     for ($j = 0; $j < sizeof($labels); $j++) {
         if ($frequency == QueryResultPeer::FREQUENCY_MONTH) {
             $labels[$j] = date('M y', strtotime($temp[$j * (sizeof($arrays[0]) - 1) / $factor]));
         } else {
             $labels[$j] = $temp[$j * (sizeof($arrays[0]) - 1) / $factor];
         }
     }
     $series->setXLabels($labels);
     $series->autoSetYLabels(5);
     $series->normalize();
     $line_chart->setSeries($series);
     if ($decorator) {
         $decorator->decorate($line_chart);
     }
     return array('values' => $arrays, 'chart' => $line_chart);
 }