title: pandas: fill a column with some numpy arrays
body: <p>I am using python2.7 and pandas 0.11.0.</p>
  
  <p>I try to fill a column of a dataframe using DataFrame.apply(func). The func() function is supposed to return a numpy array (1x3).</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  
  df= pd.DataFrame(np.random.randn(4, 3), columns=list('ABC'))
  print(df)
  
                A         B         C
      0  0.910142  0.788300  0.114164
      1 -0.603282 -0.625895  2.843130
      2  1.823752 -0.091736 -0.107781
      3  0.447743 -0.163605  0.514052
  </code></pre>
  
  <p>The function used for testing purpose:</p>
  
  <pre><code>def test(row):
     # some complex calc here 
     # based on the values from different columns 
     return np.array((1,2,3))
  
  df['D'] = df.apply(test, axis=1)
  
  [...]
  ValueError: Wrong number of items passed 1, indices imply 3
  </code></pre>
  
  <p>The funny is that when I create the dataframe from scratch, it works pretty well, and returns as expected:</p>
  
  <pre><code>dic = {'A': {0: 0.9, 1: -0.6, 2: 1.8, 3: 0.4}, 
       'C': {0: 0.1, 1: 2.8, 2: -0.1, 3: 0.5}, 
       'B': {0: 0.7, 1: -0.6, 2: -0.1, 3: -0.1},
       'D': {0:np.array((1,2,3)), 
            1:np.array((1,2,3)), 
            2:np.array((1,2,3)), 
            3:np.array((1,2,3))}}
  
  df= pd.DataFrame(dic)
  print(df)
           A    B    C          D
      0  0.9  0.7  0.1  [1, 2, 3]
      1 -0.6 -0.6  2.8  [1, 2, 3]
      2  1.8 -0.1 -0.1  [1, 2, 3]
      3  0.4 -0.1  0.5  [1, 2, 3]
  </code></pre>
  
  <p>Thanks in advance</p>