I want to iterate several maps using the atlas feature of the print composer in QGIS 3.4. The field I want the maps to iterate over has several duplicate values (ie several features belong to the same group and are labelled as such) but at the moment, atlas produces one map for each feature regardless of the fact that some have the same value in the field they're being iterated over.
What I want it to do is produce a map which is zoomed to fit all the features labelled 'A' and another map zoomed to fit all the features labelled 'B', not one map for each feature.
I could merge the features by their labels, but then I'd lose the remaining attributes which do vary and I'd like to present them in a linked attribute table, so they need to be preserved within the layer really.
All I really want QGIS to do is assign the same @atlas_featureid to all the features labelled 'A' and a different @atlas_featureid to all the feature labelled 'B', my existing set-up will do the rest.