6 Replies Latest reply on Jul 9, 2018 10:55 AM by Deepak Rai

    Transparency in Overlaid Polygon Mapping

    . Paepcke

      Using Tableau 10.5.5 I imported a .geojson file with polygons of regions within California (attached).

      Also imported is a two-column Excel sheet: City and person identifier. Multiple persons can be in

      a city. My goal is this:


      - Tableau US map at the bottom, showing county boundaries and names via the built-in map layers.

      - Semi-transparent polygons from geojson file on top of map

      - Circles at city locations with size encoding number of persons in city.


      My approach so far: use dual-axes. One axis for the circles, another for

      the polygons.


      The problems:


      1. Even setting transparency for the polygons to 1% obscures the underlying

          Tableau county borders. With just the polygon layer over the Tableau map (i.e. without

          the cities), the color transparency setting works fine. Adding the cities on top seems to cause the issue.

      2. As I run the cursor across California, I properly see the city names when I hover over

           a city. However, when the cursor is over an area without a city, the alphabetically first

           city is always listed. I would like no popup to appear when over empty areas, or at least

          an empty popup if they are unavoidable.


      How might I fix these two issues?

      Thank you for any help!


        • 1. Re: Transparency in Overlaid Polygon Mapping
          Deepak Rai

          Pl Check if you need this?



          • 2. Re: Transparency in Overlaid Polygon Mapping
            Peter Fakan

            Hi Paepcke,


            In order to understand what's happening, you need to understand that a .shp or polygon or any other kind of overlay is a special layer that sits over the top of the tableau basemap - but this is a feature, not a bug. It especially stands out if you select one of the shapes, where the rest of the shapes that overlay the map that are unselected grey out, and the selected shape 'highlights' to indicate to the screen reader that one of the overlay shapes has been selected.


            I'm not 100% sure this is your requirement, but it sounds that you are looking to indicate different regions on the basemap but not have them selectable. This might be used where the geographic boundaries might not be political ones, but for example a companies distribution area which might cross several states but not necessarily the complete state due to overlap with other distribution hubs.


            To do this you need to alter the basemap, which can be done by either connecting to a dedicated .wms server or via mapbox I think. I've only tried the former, not the latter.





            • 3. Re: Transparency in Overlaid Polygon Mapping
              . Paepcke

              Thank you both. However, Peter, if you look at my attached

              second workbook copy, and turn to sheet 2, you see that the

              very same geometry file by itself easily has its transparency

              changed: via the color button as usual. We can see the underlying

              map *and* the polygon file.


              It is only when I go dual axis to overlay the city, as I did in sheet 1

              that the transparency no longer works. Your explanation seems to

              imply that transparency for a geometry file should never work, because

              it is an overlay. Which I do want it to be.


              Thanks, Andreas

              • 4. Re: Transparency in Overlaid Polygon Mapping
                Deepak Rai

                You want this?

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                • 5. Re: Transparency in Overlaid Polygon Mapping
                  . Paepcke

                  Yes, Deepak! That's what I wanted. In your worksheet I was able to modify the

                  transparency of the polygons. Made me so happy :-)


                  I'm trying to figure out how you did this. You worked on 'Sheet 2', but there are

                  references in the measures and dimension panes to 'Sheet 1'. Is that fact relevant?

                  I'm just not clear on how you actually accomplish this solution.


                  This is absolutely enough for my needs. Just out of curiosity: when I select the Lat

                  for the city dots, and put count(anon_screen_name) onto size, the city dots don't

                  change size. Similarly, if  I put count(anon_screen_name) onto color, there seem to be

                  no color gradations, even if I change step size to, say 20. Only two colors are used:

                  light turquoise and dark blue. I can definitely live with that, but if you have time to

                  explain, I'd love to understand.


                  Thank you again,


                  • 6. Re: Transparency in Overlaid Polygon Mapping
                    Deepak Rai

                    Good it worked for you!!! then you should mark the CORRECT Answer as CORRECT for other's benefit. Isn't it? By the way I used Full Outer Join on your data with Joining on 0=1



                    1 of 1 people found this helpful