Angular 2 material implementing sort, filter and pagination

I'm trying to implement sort, filter and pagination using md-table. here is my code:

connect(): Observable<Patient[]> {
const displayPatientDataChanges = [
  this._patientDatabase.dataChange,
  this._filterPatientChange,
  this._paginator.page,
  this._sort.mdSortChange,
];

return Observable.merge(...displayPatientDataChanges).map(() => {
  const startIndex = this._paginator.pageIndex * this._paginator.pageSize;

  let displayData = this._patientDatabase.data.slice().filter((item: Patient) => {
    let searchStr = (item.firstname + ' ' + item.lastname).toLowerCase();
    return searchStr.indexOf(this.filter.toLowerCase()) != -1;
  });

I want to return both of these values but it only returns the sort function the filter and the pagination don't work.

  return displayData.splice(startIndex, this._paginator.pageSize),this.getSortedData();


});

}

 disconnect() { }

getSortedData(): Patient[] {
const data = this._patientDatabase.data.slice();
if (!this._sort.active || this._sort.direction == '') { return data; }

return data.sort((a, b) => {
  let propertyA: number|string|Date = '';
  let propertyB: number|string|Date = '';

  switch (this._sort.active) {
    case 'id': [propertyA, propertyB] = [a.id, b.id]; break;
    case 'firstname': [propertyA, propertyB] = [a.firstname, b.firstname]; break;
    case 'lastname': [propertyA, propertyB] = [a.lastname, b.lastname]; break;
    case 'dateOfBirth': [propertyA, propertyB] = [a.dateOfBirth, b.dateOfBirth]; break;
    case 'sex': [propertyA, propertyB]= [a.sex, b.sex]; break;
    case 'dateAdded': [propertyA, propertyB] = [a.dateAdded, b.dateAdded]; break;
  }

  let valueA = isNaN(+propertyA) ? propertyA : +propertyA;
  let valueB = isNaN(+propertyB) ? propertyB : +propertyB;

  return (valueA < valueB ? -1 : 1) * (this._sort.direction == 'asc' ? 1 : 1);
});
 }

How can I make the sort, filter and pagination to work?