What are you datasources, and how have you connected them in Tableau, or, are they not connected in which case, you will either need to build a data model or, blend the sources.
Three datasources all Access Databases, they are connected in Tableau and I've set the relationships for all. The data is on all three data sources is linked on post code.
To rule out any errors in Tableau, have you tried to create a view (query) in Access to handle the joins and then just connected Tableau to this view?
Also, have you just tried to plot the postcodes on a simple geomap using just number of records to create a report, just to test the data and the geomap works as expected?
And finally, exactly what is your calc, what is the expected output, and what is incorrect about it? Have you managed to break-down the calc to try to find what could be cauing the failure?
Steve hi again,
I can create the query in Access and it works fine, but for future purposes i'd like to be able to do it on the fly in tableau.
So I have 3 Access Databases as follows:
Contains polygon information such as:
Sub Polygon ID
2016 Data (just one column with some data per postcode)
2017 Estimated Data (just one column with some data per postcode)
I plot the polygons fine. I can also sum by postcode (in rows) the 2016 and 2017 data (in columns).
What I can't do, is create a simple calculated field such as:
PercentDiference = ([2017 Data]-[db2].[2016 data])/([db2].[2016 data])
The calculations are wrong. So the map is shaded wrongly....
hope this clarifies, thanks.