title: Material table datasource filter with column value
body: <p>How can I filter the material data table with specific column ? </p>
  
  <pre><code>public dataSource;
  
  
  this.dataSource = new MatTableDataSource(this.items);
          this.dataSource.filterPredicate = function customFilter(data , filter:string ): boolean {
              return (data.name.startsWith(filter));
          }
  
  applyFilter(filterValue: string) {
      filterValue = filterValue.trim(); // Remove whitespace
      filterValue = filterValue.toLowerCase(); // MatTableDataSource defaults to lowercase matches
      this.dataSource.filter = filterValue;
  }
  </code></pre>
  
  <hr>
  
  <p>The above code is not working,  when I type returns as no data is matched. </p>