/**
  * Display a listing of the resource.
  *
  * @return \Illuminate\Http\Response
  */
 public function index()
 {
     $students = Student::all();
     $marks = Mark::all();
     foreach ($students as $student) {
         $marks_count = 0;
         $marks_value = 0;
         foreach ($marks as $mark) {
             if ($mark->student_id == $student->id) {
                 $marks_count++;
                 $marks_value += $mark->value_2;
             }
         }
         if ($marks_count != 0) {
             $student['mark_avg'] = $marks_value / $marks_count;
         } else {
             $student['mark_avg'] = 0;
         }
     }
     $students = $students->sortByDesc('mark_avg');
     $students = $students->splice(0, 10);
     return view('students.index', ['students' => $students]);
 }