title: How to get previous row value in DAX power bi
body: <pre>
  family  month  qty  prev_qty
  
  A        M07   5     5
  A        M08   6     5
  A        M09   7     6
  B        M07   10    10
  B        M08   11    10
  B        M09   12    11
  </pre>
  <p>Previous qty is the column i want to populate in my dashboard. I used dax like earlier and also created index but its not helping. Any DAX function for this table to find the previous row value?</p>