title: Remove Outlier Row from pandas dataframe
body: <p>What is the Efficient way to remove outlier from a pandas dataframe? 
  I have a pandas dataframe where i need to remove outlier points from the dataframe.</p>
  
  <pre><code> X1       X2              X3              X4
  228.0   4474.91836735   3507.15151515   6625.0
  77.0    468.0           582.0           549.0
  160.0   9.0             3507.15151515   6625.0
  36.0    250.0           3507.15151515   6625.0
  52.0    3.0             3.0             223.0
  78.0    998.0           3507.15151515   6625.0
  </code></pre>
  
  <p>I tried with the solution in <a href="https://stackoverflow.com/questions/23199796/detect-and-exclude-outliers-in-pandas-dataframe">link</a>
  but no points were removed. Even a sklearn implementation for the same will be useful.</p>