The filled map mark type uses geocoding to fill a polygon with a color based on data. The primary use of the filled map mark type is for creating choropleth maps (also known as thematic maps or data maps). The area to be filled is defined by the geographic fields used in the view. Tableau displays data using a filled map when:
A geographic dimension is on the Detail
target on the Marks card, along with Latitude and Longitude on the Rows and Columns shelves.
A measure or continuous dimension is added to the Color target.
You select Filled Map from the Mark menu.
The polygon for each state is filled with a color based on the profit for that state. The profit in Montana is low (in fact, negative) while the profit in Texas is high.
Another way to use the Filled Map mark type is when you are plotting two measures against each other. By default, placing measures on both the Rows and Columns shelves creates a scatter plot. However, adding a geographic dimension allows you to change the mark type to Filled Map. Each mark becomes the area defined by the geographic field. For example, the view below shows Sales versus Profit for a selection of states. Rather than showing a round mark with a label for each state, the view uses the Filled Map mark type to draw the outline of each state. While this works well for recognizable areas, it is not the best choice for areas that are similar in shape or difficult to recognize.