title: Moving average in Pandas
body: <p>I have a csv file with 3 columns and I want to get the moving average of 1 column.
  I want to create a new column with the moving average.</p>
  
  <pre><code>import pandas as pd
  
  df= pd.read_csv('csv',usecols=['speed','col2', 'col3'])
  df['MA'] = df.rolling( window=5, on='speed').mean
  print(df)
  </code></pre>
  
  <p>It doesnt show me any column anymore. Only the Index and ... . </p>
  
  <pre><code>1   ...
  2   ...
  3   ...
  3   ...
  4   ...
  
  [4 rows x 4 columns]
  </code></pre>
  
  <p>If I change to: </p>
  
  <pre><code>df= df.rolling(window=5, on='speed').mean
  print(df)
  </code></pre>
  
  <p>It only returns me this:</p>
  
  <pre><code>&lt;bound method Rolling.mean of Rolling [window=5,center=False,axis=0,on=speed]&gt;
  
  Process finished with exit code 0
  </code></pre>