All marks except lines and shapes have a black border. When your view contains a lot of data, mark borders can blend together and sometimes make it hard to identify colors. A common example is a dense Heat Map or scatter plot. You can turn off the mark borders to clean up the view and make it possible to find hidden insights.
The view below is a Heat Map showing product category performance in terms of profit and discount by region and market segment. The size of each mark represents the total discounts, while gross profit is encoded as color. With the mark borders turned on, it is difficult to distinuguish the profitability of the product categories with fewer sales.
This view shows the SUM of the Sales field for each product in Product Sub-Category 2. You can scroll through the list of thousands of products and search for the ones you are interested in, or you can create a computed set containing just the top products.
To turn the mark borders on and off, on the Marks card, click the Color menu arrow, and then in the Border dropdown, select a color for the mark borders. If you do not want borders, keep the default setting of None.
You can see that without the mark borders, some findings become more visible. For instance, it is now quite clear that the tables in the eastern region are bringing debt rather than profit.
Note: Another way to inspect dense data is to manually set the order in which marks are drawn. For example, in a scatter plot where marks overlap, you can re-order the marks by rearranging the color legend.
