public function search_statistic($field_id)
 {
     $trainings = SeekTraining::all();
     $training_array = array();
     foreach ($trainings as &$training) {
         foreach ($training->fields as $field) {
             if ($field->id == $field_id) {
                 $training->municipalities;
                 $training['region'] = Region::where('id', '=', $training->municipalities[0]->region_id)->get();
                 $training_array[] = $training;
             }
         }
     }
     $country_array = array('quantity' => 0);
     $regions_array = array();
     $regions_id_array = array();
     foreach ($training_array as $training) {
         $country_array['quantity'] += $training['quantity'];
         if (!in_array($training['region'][0]['id'], $regions_id_array)) {
             $regions_id_array[] = $training['region'][0]['id'];
             $regions_array[$training['region'][0]['id']] = array('name' => $training['region'][0]['name'], 'quantity' => $training['quantity']);
         } else {
             $regions_array[$training['region'][0]['id']]['quantity'] += $training['quantity'];
         }
     }
     $municipalities_array = array();
     $municipalities_id_array = array();
     foreach ($training_array as $training) {
         if (!in_array($training['municipalities'][0]['id'], $municipalities_id_array)) {
             $municipalities_id_array[] = $training['municipalities'][0]['id'];
             $municipalities_array[$training['municipalities'][0]['id']] = array('name' => $training['municipalities'][0]['name'], 'quantity' => $training['quantity']);
         } else {
             $municipalities_array[$training['municipalities'][0]['id']]['quantity'] += $training['quantity'];
         }
     }
     return json_encode(['regions' => $regions_array, 'municipalities' => $municipalities_array, 'country' => $country_array]);
 }