public static function getAverageFields(CustomDataPosition $pos, array $params = array())
 {
     $filter = new CustomDataFilter($pos);
     $filter->field(null);
     $fields = $pos->getFieldsForClassPath(self::$classPath);
     foreach ($fields as $field) {
         $fieldName = Sanitize::saveDb($field->getFieldName());
         $filter->fieldCalculation($fieldName, "AVG({$fieldName})");
     }
     foreach ($params as $field => $value) {
         $filter->condition($field, $value);
     }
     $result = $filter->execute();
     if ($result) {
         $data = new CustomData($pos);
         $row = Database::getObject()->fetchAssoc($result);
         if ($row) {
             $data = new CustomData($pos);
             $data->set($row, true, $fields);
             return $data->getFields(array_keys($fields));
         }
     }
     return array();
 }