Calculations open up amazing possibilities in Tableau. You are no longer confined to the fields in the source data. With calculations, you can extend the data by adding new dimensions and measures, fix bad or poorly formatted data, enhance the user experience with parameters for user input and calculations that enhance the visualizations, and you can achieve flexibility that makes data blending work in situations where the data might have made it difficult or impossible otherwise.

The key to using calculated fields is an understanding of the three levels of calculations in Tableau. Row-level calculations are performed for every row of source data. These calculated fields can be used as dimensions, or they can be further aggregated as measures. Aggregate-level calculations are performed at the level of detail defined by the dimensions present in a view. They are especially helpful, and even necessary, when you must first aggregate components of the calculation before performing additional...