I had to rewrite this to understand what it's doing. Chain and good variable names are you friend, ben.

```coffee
averagePointsByDomain = _.chain(rankings)
  .groupBy('domain')
  .map (rankings, domain) ->
    totalPoints = _.reduce rankings, (memo, {points}) ->
      memo + points
    , 0
    [
      domain
      rankings.length
    ]
```