Occasionally, the columns included in a data table do not allow you to perform all necessary operations, or to create the visualizations needed to fully explore the data table. However, in many cases the necessary information can be computed from existing columns by using the mathematical and logical expressions provided by the Insert Calculated Column tool.
Note: A calculated column is treated like any other column and its contents are static during all further analysis. If you want to use expressions that change during filtering of your data table, you should instead use custom expressions that are defined where you need them (for example, select Custom Expression... from the right-click menu on the axis selector).
See also:
How to Insert a Calculated Column