title: How to group mongodb count results by regular expresions?
body: <p>I have a small database in which I stored some tweets and I'm trying to find out which was the most popular keyword from a previously selected set of words.</p>
  
  <p>The structure of the documents is:</p>
  
  <pre><code>{
       "Username": status.author.screen_name,
       "Tweet": status.text,
       "Retweets": status.retweet_count,
       "Favorites": status.favorite_count,
       "Followers": status.user.followers_count,
       "Background-Color": status.user.profile_background_color,
       "Date-Created": status.user.created_at,
       "Location": status.user.location,
       "Verified-Status": status.user.verified,
       "Geo-Enabled": status.user.geo_enabled,
       "Possibly-Sensitive": status.user.geo_enabled
  }
  </code></pre>
  
  <p>and the results are based on the Tweet field</p>
  
  <p>I've already made individual queries with regular expressions finding how many times each word appears, but I haven't figured out a way to get some output like:</p>
  
  <pre><code>{ 
       Keyword: "something",
       Count: 1200,
  }
  </code></pre>