I have created a layout atlas based on a geographic layer containing defined store 'catchments' (ie as polygons).
Each atlas 'page' shows just the relevant catchment region.
For each atlas feature, I also want to customise a thematic representation of each store's market share by postcode. This runs from a separate layer which is based on postcode regions and has a field for each store showing the market share within each postcode.
I am trying to reference the field name (in the picture below the field name is 'Albury_mkt') dynamically as a concatenation of the atlas page name ('Albury') and the text string "_mkt".
If successful, each atlas page will show the thematic only for the relevant region.
I have tried to use the function concatenate(@atlas_pagename,'_mkt') but this doesn't seem to parse properly.