title: python, pandas: InvalidIndexError when creating dataframe
body: <p>I have been exploring the <a href="https://www.kaggle.com/c/titanic/data" rel="nofollow noreferrer">titanic dataset</a>. I am trying to create a 
  <code>dataframe</code> which will have the ages of the people who survived the titanic sinking, and those who didn't, in two separate columns.</p>
  
  <pre><code>    train = pd.read_csv('train.csv')
      test = pd.read_csv('test.csv')    
      whole = pd.concat([train, test])
      df = pd.DataFrame({'survived': whole['Age'][whole['Survived'] == 1],
                         'died': whole['Age'][whole['Survived'] == 0]})
  </code></pre>
  
  <p>But I am getting this error</p>
  
  <blockquote>
    <p>pandas.indexes.base.InvalidIndexError: Reindexing only valid with
    uniquely valued Index objects</p>
  </blockquote>
  
  <p>What am I doing wrong?</p>