2 Replies Latest reply on Apr 19, 2018 4:36 AM by David Holderness

    (10.5) merging polygons within a Spatial File

    David Holderness

      Hi All


      Using the .tab download found here https://data.gov.uk/dataset/ccg-map


      I have a list of all CCG codes, their names and polygons that map them on to the UK Map.


      However since this was created three CCGS have merged,


      NHS Central Manchester (00W)

      NHS North Manchester (01M)

      NHS South Manchester (01N)


      Has become NHS Manchester CCG (14L)


      Most analytics I am receiving now use the code 14L.


      I tried creating a calculated field, assigning 14L to the previous three and an unaltered code to any others and then blending with the analytics I receive. When i use a cross table the data displays fine however when i try to map it data doesn't show (see below - the field i am using to shade the polygons displays successfully on a cross tab but is blank on the map)


      tableau problem.PNG


      Ideally i would be like to merge the three polygons and assign the new polygon the name NHS Manchester CCG with the code 14L, however if there is a way to get my method working that'd be great too.


      Any help much appreciated

        • 1. Re: (10.5) merging polygons within a Spatial File
          Sarah Battersby

          Hi David,

          I grabbed a copy of the .tab file that you are using and mapped it out myself to see if I could make something work.  I used a calculated field with a CASE statement to re-label the regions and then used an LOD calculation to aggregate the values for my regions (since I wanted the three polygons that became 14L to be grouped together).


          That might work for you.  At least on my test map the aggregation worked just fine (just a sum(number of records) in my case since I didn't have any attributes to join in).  My simple workbook is attached for reference.


          If this isn't getting you closer to a solution, could you attach your workbook so that I could just experiment on that using some real data?




          My LOD calc: {fixed [new code]: sum([Number of Records])}

          My Case statement to re-label:

          case [CC Gcode]

              when '00W' then '14L'

              when '01M' then '14L'

              when '01N' then '14L'

          else [CC Gcode]



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          • 2. Re: (10.5) merging polygons within a Spatial File
            David Holderness

            Thanks Sarah this did the trick