public function missing($alias, $field)
    {
        $aggregation = new MissingAggregation($alias, $field);

        $this->append($aggregation);
    }
public function missing($alias, $field)
    {
        $aggregation = new MissingAggregation($alias, $field);

        $this->append($aggregation);
    }
public function missing ( $ alias , $ field ) { $ aggregation = new MissingAggregation ( $ alias , $ field ) ; $ this -> append ( $ aggregation ) ; }
Add an missing aggregate.

@param string $alias
@param string $field
Add an missing aggregate .