I, too, have struggled with this. I really hope Version 9 makes this a bit easier to do. Have you tried setting up your own GeoServer? It is possible to do what you want, but it requires some education in GIS tools. I've been unable to try too much yet, as some corporate security setting is preventing me from getting it set up properly.
As you didn't have the DBF (Feature File) joined, I created a duplicate of [Health_Authority_ID] and made a CF STR([Health_Authority_ID]). I generated a dual-axis by adding Longitude to the column shelf and then in the second mark card changed the type to circle and labelled my CF. I also knocked the transparency down to 10% so you can see the background map layer.
Note, all I have done here is plot where the labels are; not where your features are.
Thanks for your reply, Allan.
I think this would work, but unfortunately I'm wanting to plot about 200 points and sometimes as many as 500. What's the best way to link my features with the Health Authority regions to opitimize the dashboard refresh speed? Or, with this many features, would another solution be required to improve the refresh speed?
Tableau is able to plot about 4 million marks without an issue in V8. V8.1 64-bit will help, I've rendered out 60,000,000 marks on a dashboard with the beta. I wouldn't be concerned about dashboard refreshing speed with those numbers.
If you chose to: you could incorporate your original SHP file into a WMS server, and then you would only need to plot out the 500 features, rather than waiting for Tableau to render the polygon. Here's the link to the tutorial.
I think I've figured it out, thanks to your suggestions. See attached.
One last issue... Whenever I click on a specific facility in the list to the left of the map, the regional shading on the map disappears. Do you know of any ways to prevent this from happening?
P.S. As an aside to your point about WMS - there is a WMS available through the BC gov't (http://openmaps.gov.bc.ca/mapserver/admin-boundaries?service=wms&request=getcapabilities&version=1.1.1) which shows the Health Authority regions, but unfortunately it's not the prettiest, it's slightly distorted and doesn't show the topography. Not huge barriers, but I was hoping for something prettier
BC RegionsandFacilities.twbx 2.9 MB
When you created the dashboard filter, it's not filtering on the polygon, just the circle mark. That's why it is "disappearing".
However, I went about this a different way:
If you follow my tutorial, here's the steps I took.
1. Cascade WMS Open Maps as per your link
2. Cascade WMS from US Naval Labs and choose OpenStreetMap
3. Changed the datum of US Naval Labs from EPSG:3857 to EPSG:3824
4. Changed the datum of WMS Open Maps as per your link from EPSG:3005 to EPSG:3824
5. I created a layer group called BC Health & OSM and set the datum as EPSG:3824
5. Dragged Longitude to columns, Latitude to rows
6. Dragged Facilities to detail
7. Dragged Facilities to label
8. Created a quick filter (should have used a parameter to get rid of the null option, but didn't have time)
Notes: I could have used a SHP file (say Natural Earth Admin 1) rather than OSM as the background map. I could have ingested the BC Health Districts SHP file and styled it rather than using a cascaded WMS server. (Into my own Geoserver).
That would enable local working rather than using hosted services, and I could style those as I liked (Using AtlasStyler).
I now have a background map, middle layer, and a foreground layer of analysis. No dual axis required.
Note: you could contact Craig Bloodworth at The Information Labs, who would post the SHP file to Tableau Mapping and share it with the community; or; you could have asked Urban Mapping to host the SHP file for you (although this is a paywalled service).