Starting with Tableau V9, the calculated field window shows up a white, modeless window. Prior to Tableau V9, you needed to close the calculated field window before you could do anything else with Tableau. With the modeless window, you can continue to work on your tasks, such as dragging fields to shelves, while the calculated field editor is open. The modeless window also allows you to drag and drop fields from the sidebar onto the calculated field window.
In the calculated field window, you have to specify the calculated field name and an expression (or formula).This expression can include the following:
Data fields from your data source(s)
Functions
Parameters
Comments
Comments are optional but highly recommended. Tableau supports single line comments. Anything that starts with two forward slashes, //, will be considered a single line comment and will not be executed by Tableau, as shown next:
If there are any errors, there will be a message at the bottom of the editor that will show the error message. The formula itself will have a red squiggly underline to signal the error in the syntax. This is shown in the following screenshot:
