What is the purpose of Field?
Selects the field or expression that contains the data values. The drop-down list displays all the applicable fields in the table selected when creating the theme.
When is Field active?
When a Ranged Thematic layer is selected in Explorer or Layers window.
How do I access Field?
On the THEME tab, in the Ranged Style group, click Field, and click the required field from the list.