title: Merge two Dataframes with different structures
body: <p>I am trying to combine two dataframes with each other. But I am stuck on the logic (maybe I looked too long to the problem).</p>
  <p><strong>Problem:</strong>
  DF1 is in a format like this:</p>
  <pre><code>Country       ID    March    April  May  June 
  Netherlands   A      10       20     15   14 
  Netherlands   B      15       18     10    4
  Germany       C       9        8      3    1 
  </code></pre>
  <p>Then, I have another dataframe:</p>
  <p>DF2</p>
  <pre><code>Country      ID    Month   Number
  Netherlands  A     March     8  
  Netherlands  A     March     28  
  Netherlands  B     April     18  
  Germany      C     Jan       9
  </code></pre>
  <p>I would like to merge these two columns (in the same format as DF1).
  My assumption was that is should be something like, group by (Country + ID), and then (Month as column, and SUM the Number). - but as said before, I am confussed.</p>
  <p>Desired output:</p>
  <pre><code>Country       ID    March    April  May  June   df2_Jan  df2_March   df2_April
  Netherlands   A      10       20     15   14       0       36 #8+28     0
  Netherlands   B      15       18     10    4       0        0          18
  Germany       C       9        8      3    1       9        0           0
  </code></pre>
  <p>Hope that you can help me. Thanks a lot in advance!</p>