Multiple labels from same variable using QGIS

Question

How can I have a set of labels for a location, where the variables are within a single column?

What I am hoping for is to have placement of 'concentration' followed by depth at each location shown on label.

Example of my data:

Loc_ID (1, 1, 1, 2, 2, 2...) Depth_m (0.2, 0.5, 1.0, 0.2, 0.5, 1.0) Conc. (1, 0.2, <LOR, 1 ,no data, 0.2) etc...

I have tried CASE and coalesce. However, in an instance where there is no data, the label shows an empty line, which is not required.

I am using QGIS.

Answer 1

Sorry if I did not understand you properly; I thought you might want an expression like:

CASE 
WHEN "Conc" != 'no data'
THEN 'Loc_ID: '  + to_string("Loc_ID")  + '\n' + 
     'Depth_m: ' + to_string("Depth_m") + '\n' + 'Conc: '    + to_string("Conc")
ELSE 'Loc_ID: '  + to_string("Loc_ID")  + '\n' + 'Depth_m: ' + to_string("Depth_m")
END 

in the Field Calculator -

Which will produce a new field for the label:

---

[UPDATE]

To make a "grouped" label at each 'Loc_ID', you can use concatenate() function.

Using the previously made "Label" field, the expression would be:

concatenate("Label" , group_by:= "Loc_ID", concatenator:= '\n', order_by:= 'Depth_m')

Given this is what you are up to, the expression for "Label" field should be simplified as below:

CASE WHEN  "Conc" != 'no data'
THEN 'Depth_m: ' + to_string("Depth_m") + ' , ' + 'Conc: ' + to_string("Conc")
ELSE 'Depth_m: ' + to_string("Depth_m")
END 

The final attribute table becomes:

Please use the `"oneLabel"' field to add the label.