title: Using Panda to create new column with data from another row and column
body: <p>I'm trying to create a new row for &quot;new confirmed cases&quot; using the current row 'confirmed' - yesterday 'confirmed'. Confirmed is cumulative.</p>
  <p>my data is as shown</p>
  <pre><code>Country,Date,Confirmed,Deaths,Recovered,Active
  China,2020-01-21,10,5,1,100
  China,2020-01-22,20,10,2,104
  China,2020-01-23,30,15,3,116 
  France,2020-01-21,20,5,1,100
  France,2020-01-22,30,10,2,118
  France,2020-01-23,40,15,3,138
  
  
  </code></pre>
  <p>Output wanted</p>
  <pre><code>Country,Date,Confirmed,Deaths,Recovered,Active,New Confirmed
  China,2020-01-21,10,5,1,100,0
  China,2020-01-22,20,10,2,104,10
  China,2020-01-23,30,15,3,116,10
  France,2020-01-21,20,5,1,100,0
  France,2020-01-22,30,10,2,118,10
  France,2020-01-23,40,15,3,138,10
  </code></pre>
  <p>I know how to add a new row if using data from the same row but not sure how to use data from another row. Any tips or advice would be appreciated.</p>