$ AVG沒有返回平均

Question

，這是我的代碼：

//Build the query 
     //match only records in cluster 1 
     DBObject match = new BasicDBObject("$match", new BasicDBObject("clusterId",_id)); 
     //the projected result must be : clusterId, squeezePlay, weakShowdown, playsWithFriends 
     DBObject projectFields = new BasicDBObject("clusterId",1); 
     projectFields.put("squeezePlay", 1); 
     projectFields.put("weakShowdown", 1); 
     projectFields.put("playsWithFriends", 1); 
     DBObject project = new BasicDBObject("$project", projectFields);   
     //the groupfields are the average of each category grouped by clusterId 
     DBObject groupFields = new BasicDBObject("_id",new BasicDBObject("clusterId","$clusterId")); 
     groupFields.put("squeezePlay", new BasicDBObject("$avg","$squeezePlay")); 
     groupFields.put("weakShowdown", new BasicDBObject("$avg","$weakShowdown")); 
     groupFields.put("playsWithFriends", new BasicDBObject("$avg","$playsWithFriends")); 
     DBObject group = new BasicDBObject("$group", groupFields); 


     AggregationOutput output = coll.aggregate(match, project, group); 

在數據庫中的球員如下：

 Player p1 = new Player(); 
     p1.SetClusterID(1); 
     p1.SetId("Player 1"); 
     p1.SetNumberOfPlays(21); 
     p1.SetPlaysWithFriends(22); 
     p1.SetSqueezePlay(23); 
     p1.SetWeakShowdown(24); 

     Player p2 = new Player(); 
     p1.SetClusterID(1); 
     p2.SetId("Player 2"); 
     p2.SetNumberOfPlays(11); 
     p2.SetPlaysWithFriends(12); 
     p2.SetSqueezePlay(13); 
     p2.SetWeakShowdown(14); 

輸出對子級爲：（17.0，18.0，19.0） 但相反，我得到："Averages are: 23.0 22.0 24.0"這對我來說更像是一個Max（或者也許只是玩家1的結果）......我不知道。

Answer 1

錯字錯誤：

你應該實例玩家P2