title: Average of Dataframe columns
body: <p>I want to get the average GDP of each country across the years, the columns 2006, 2007...2015 contain the GDP numbers... My code returns an error that mean(axis=1) needs at least 1 variable, and 1 has been assign to it... which is weird..I also find it weird that we are using mean instead of avg, but coulnd't find an avg function for groupby </p>
  
  <p>here is my code</p>
  
  <pre><code>    Top15 = ANSWER
      Top15 = Top15[['Country', '2006', '2007', '2008', '2009', '2010', 
      '2011', '2012', '2013', '2014', '2015']]
      return Top15.groupby('Country').agg({"avg": np.mean(axis=1)})
  </code></pre>