title: Indexing on Pandas Grouby Data frame Gives error
body: <p>I have a Pandas GroupBy Data frame named <strong>ratings_by_title</strong> that looks like the following:</p>
  
  <pre><code>title
  $1,000,000 Duck (1971)                37
  'Night Mother (1986)                  70
  'Til There Was You (1997)             52
  'burbs, The (1989)                   303
  ...And Justice for All (1979)        199
  1-900 (1994)                           2
  10 Things I Hate About You (1999)    700
  101 Dalmatians (1961)                565
  101 Dalmatians (1996)                364
  12 Angry Men (1957)                  616
  </code></pre>
  
  <p>I am trying to filter out the titles having a rating of >=250
  so,</p>
  
  <p>I tried the following <code>active_titles = ratings_by_title.index[ratings_by_title &gt;= 250]</code></p>
  
  <p>But,This gives an error in iPython saying</p>
  
  <blockquote>
    <p>AttributeError: Cannot access attribute 'index' of 'DataFrameGroupBy' objects, try using the 'apply' method</p>
  </blockquote>
  
  <p>Could somebody help me understand what's going on?</p>