title: Pandas: Insert column according to index values
body: <p>I have the following example data</p>
  
  <pre><code>In [1]: table[['id', 'age']]
  Out[1]: 
     id  age
  0   1   12
  1   2   13
  2   3   14
  3   4   15
  4   5   16
  5   6   17
  6   7   18
  7   8  NaN
  8   9   20
  </code></pre>
  
  <p>ad the following <code>np.array</code></p>
  
  <pre><code>In [2]: data
  Out[2]: 
  array([[  1.,   3.,  21.],
         [  2.,   4.,  21.],
         [  3.,   5.,  22.],
         [  4.,   5.,  22.],
         [  5.,   4.,   2.]])
  </code></pre>
  
  <p>and would like to concatenate the <code>data</code> to the <code>table</code> according to the <code>id</code>.</p>
  
  <p>For example the result should look like:</p>
  
  <pre><code>id  age
  0   1   12  3     21
  1   2   13  4     21 
  2   3   14  5     22
  3   4   15  5     22
  4   5   16  4     2
  5   6   17  
  6   7   18  
  7   8  NaN  
  8   9   20  
  </code></pre>
  
  <p>I can loop over <code>zip(table,data)</code> and work line by line, but I thought it could be done in a more <em>concise</em> way  </p>