Remember that the two keys to good structure are having a level of detail that is meaningful and having measures that match the level of detail or that are possibly at higher levels of detail. Measures at lower levels tend to result in wide data, and can make some analysis difficult or even impossible. Measures at higher levels of detail can, at times, be useful. As long as we are aware of how to handle them correctly, we can avoid some pitfalls.
Consider, for example, this data (included as Apartment Rent.xlsx in the Chapter 9 directory), which gives us a single record each month per apartment:
The two ...
