title: Must have equal len keys and value when setting with an iterable
body: <p>I have two dataframes as follows:</p>
  <pre><code>leader:
      0 11
      1 8
      2 5
      3 9
      4 8
      5 6
      [6065 rows x 2 columns]
  
  DatasetLabel:    
      Unnamed: 0      0    1  ....    7     8    9  10  11  12  
      0               A    J  ....    1     2    5 NaN NaN NaN  
      1               B    K  ....    3     4   NaN  NaN NaN NaN  
  
      [4095 rows x 14 columns]
  </code></pre>
  <p>The Information dataset column names 0 to 6 are DatasetLabel about data and 7 to 12 are indexes that refer to the first column of leader Dataframe.</p>
  <p>I want to create dataset where instead of the indexes in DatasetLabel Dataset I have the value of each index from the leader dataset, which is <code>leader.iloc[index,1]</code></p>
  <p>How can I do it using python features?</p>
  <p>The output should look like:</p>
  <pre><code> DatasetLabel:    
          Unnamed: 0      0    1  ....    7     8    9  10  11  12  
          0               A    J  ....    8     5    6 NaN NaN NaN  
          1               B    K  ....    9     8   NaN  NaN NaN NaN  
  </code></pre>
  <p>I have come up with the following, but I get an error:</p>
  <pre><code>    for column in DatasetLabel.ix[:,8:13]:
          DatasetLabel[DatasetLabel[column].notnull ()]=leader.iloc[DatasetLabel[DatasetLabel[column].notnull ()][column].values,1]
  </code></pre>
  <p>Error:</p>
  <pre><code>ValueError: Must have equal len keys and value when setting with an iterable
  </code></pre>