Final answer:
In a Level of Detail expression, specific LOD keywords such as INCLUDE, EXCLUDE, and FIXED are used to indicate calculations at different levels of detail compared to the view level. These keywords determine how dimensions are factored into these calculations in tools like Tableau.
Step-by-step explanation:
When implementing a Level of Detail (LOD) expression in data visualization tools such as Tableau, you use specific LOD keywords to indicate the calculation that is occurring at a different level of detail compared to the view level. These keywords include INCLUDE, EXCLUDE, and FIXED. The INCLUDE keyword allows the calculation to consider both the dimensions specified in the view and additional dimensions. The EXCLUDE keyword excludes certain dimensions from the calculation, regardless of the view. The FIXED keyword computes the calculation at the specified level of detail, regardless of the dimensions present in the view.
For example, if you wish to calculate the average sales per region regardless of the filters applied to the view, you would use the FIXED keyword in your LOD expression like this: {FIXED [Region]: AVG([Sales])}. This would ensure that the average sales per region are computed at the region level, without considering other dimensions like categories or sub-categories that might be present in the view or filters.