public function index()
 {
     $field['numberFields'] = array_merge(self::$FIELDS['measurements']['numberFields'], self::$FIELDS['stations']['numberFields']);
     $field['nameFields'] = self::$FIELDS['stations']['nameFields'];
     $field['showOnlyFields'] = ['events'];
     foreach (self::$FIELDS['measurements']['numberFields'] as $numberField) {
         $fieldValues[$numberField]['min'] = Measurement::min($numberField);
         $fieldValues[$numberField]['max'] = Measurement::max($numberField);
     }
     foreach (self::$FIELDS['stations']['numberFields'] as $numberField) {
         $fieldValues[$numberField]['min'] = Station::min($numberField);
         $fieldValues[$numberField]['max'] = Station::max($numberField);
     }
     return view('weather.export', ['fields' => $field, 'stations' => Station::all()->sortBy('name'), 'countries' => Station::distinct('country')->lists('country')->sort(), 'fieldValues' => $fieldValues]);
 }