title: Pandas warning when using map: A value is trying to be set on a copy of a slice from a DataFrame
body: <p>I've got the following code and it works. This basically renames values in columns so that they can be later merged.</p>
  
  <pre><code>pop = pd.read_csv('population.csv')
  pop_recent = pop[pop['Year'] == 2014]
  
  mapping = {
          'Korea, Rep.': 'South Korea',
          'Taiwan, China': 'Taiwan'
  }
  f= lambda x: mapping.get(x, x)
  pop_recent['Country Name'] = pop_recent['Country Name'].map(f)
  </code></pre>
  
  <blockquote>
    <p>Warning:
    <em>A value is trying to be set on a copy of a slice from a DataFrame.
    Try using .loc[row_indexer,col_indexer] = value instead
    See the the caveats in the documentation: <a href="http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy">http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy</a>
      pop_recent['Country Name'] = pop_recent['Country Name'].map(f)</em></p>
  </blockquote>
  
  <p>I did google this! But no examples seem to be using map, so I'm at a loss...</p>