$r = Statistics::aggregate(array(
                array('$match' => array(
                    'date' => array(
                        '$gte' => new MongoDate($dateStart),
                        '$lte' => new MongoDate($dateEnd)
                    ),
                    'type' => $type
                )
                ),
                array(
                    '$project' => array(
                        'string2' => 1,
                        'month' => array('$month' => '$date'),
                        'year' => array('$year' => '$date'),
                        'week' => array('$week' => '$date'),
                    )
                ),
                array(
                    '$group' => array(
                        '_id'=>array(
                            'month' => '$month',
                            'year' => '$year',
                            'week' => '$week',

                        ),
                        'number' => array('$sum' => ($type == "buyCredits" ? '$string2' : 1) ),

                    )
                ),
                array('$sort' => array('_id.year' => 1, '_id.month' => 1, '_id.week' => 1)),


            ));