There are a few parts to doing this:
- For your companies - do you only have addresses? To map those in Tableau you would need latitude and longitude values. Tableau does not natively geocode from addresses. There are some online geocoding tools that you can use to translate the addresses to lat / lon. I don't have one in particular to recommend, but if you search for online free geocoding you will probably find some options.
- For the congressional districts - you can geocode these locations in Tableau if you have a dataset that tells Tableau which ones to add to the viz. There isn't a direct way to enrich your company data with the attributes of Tableau geocoding polygons.... BUT... an upcoming release will have an option for spatial intersection of points and polygons, so if you have a geographic file of congressional districts (you can get this from the US Census: Cartographic Boundary Shapefiles - Congressional Districts - Geography - U.S. Census Bureau) and you have point data for your companies it will soon be able to join those in Tableau. I'm not sure on the exact date for the release so can't give that, but we showed off some examples of the feature today in a Dev Office Hours with the Maps Team (Dev Office Hours: Mappy Hour – Working with Spatial Data in Tableau). The recording will be linked to that page soon.
I'm looking to do the same thing as DJ and I do have Latitude and Longitude values in my data set for each company. Even with these values I'm not seeing how to use the Congressional District in the map. I'm also still on 10.5 so I don't know if that makes a difference. I've also tried getting the shape file from the census.gov website and have not had any luck with that either.
With 10.5 you should be able to just download the Census Congressional Districts from their Cartographic Boundary files. Once that is unzipped, just add the shapefile to Tableau and you can render it with the Geography measure. You'll want to also put a unique ID on detail (e.g., GEOID) so that the individual districts are separated out on the map. That will at least get you to the part of being able to see the shapefile in Tableau.
In terms of making the dual axis map, you'll want to join your table with lat/lon values to the Shapefile. You can do that directly in Tableau. Try the instructions in Dual Axis Mapping - Many Ways for how to combine spatial file + csv. It should just involve setting up a full outer join on non-matching fields (I use 'calculated fields' in the join dialog and set one side of the join equal to 1 and the other to 0...that guarantees that I get all rows from the spatial data and all rows from the lat/lon data). After that, it should just be setting up the dual axis map.
Let me know if you find problems along the way.