For this, you can use the grouping function in Tableau
Right click on the field you want to group with (in this case I'm assuming it's county), hover over create and then click on "Group". Then Ctrl+click on Atlanta, Marietta and Columbus, click Group, and rename it to Georgia. Do the same with the California counties. Click OK at the bottom of the dialogue window, and you should now have a new field that you can use to display data for the two states.
Hope this helps,
Sum Group Data.twbx 38.8 KB
Thank you. That was helpful. How do I create a larger dot on a line graph?