title: How is the feature score(/importance) in the XGBoost package calculated?
body: <p>The command <code>xgb.importance</code> returns a graph of feature importance measured by an <strong>f score</strong>.</p>
  
  <p>What does this <strong>f score</strong> represent and how is it calculated?</p>
  
  <p>Output:
  <a href="https://i.stack.imgur.com/7ow0x.png" rel="noreferrer"><img src="https://i.stack.imgur.com/7ow0x.png" alt="Graph of feature importance"></a>
  <a href="https://i.stack.imgur.com/7ow0x.png" rel="noreferrer">Graph of feature importance</a></p>