public function corrUnemployment($level, $levelid = null)
 {
     $rateUnemployment = [];
     $attrition = [];
     $batches = [];
     $results = Correlation::getUnemployment($level, $levelid);
     foreach ($results as $result) {
         array_push($batches, $result->batch);
         $rateUnemployment[$result->batch] = $result->ratio;
         $attrition[$result->batch] = $result->dropouts;
     }
     return round($this->getCorrelation($rateUnemployment, $attrition, $batches), 2);
 }