How to reduce / aggregate multiple fields in a table? This does not seem efficient:

```
r.object(
  'favorite_count', 
  r.db('twitterdb').table('tweets').map(tweet => tweet('favorite_count')).avg().round(),
  'retweet_count',
   r.db('twitterdb').table('tweets').map(tweet => tweet('retweet_count')).avg().round()
  )

```

(Expected) Result: 

```
{

    "favorite_count": 17 ,
    "retweet_count": 156

}

```