Dynamic Label for Measure in Bar Chart

[wttaryde]

I need to have dynamic labels in the legend for my stacked bar chart.

Example data:

Company, Qnum, Response, Subtext
Albertsons, BL5.1, 1123, Mail
Albertsons, BL5.2, 12345, Internet
Safeway, BL5.1, 12345, Mail
Safeway, BL5.2, 123455, Internet

My measure expressions are:

Sum({$<Qnum={"BL5.1"}>}Response)
Sum({$<Qnum={"BL5.2"}>}Response)

resulting in stacked bar

Right now my label for each measure is just text: "Mail" or "Internet". 

I'd like my label to automatically populate so that when the measure uses BL5.1 my label = Mail; for BL5.2 my label = Internet; without me having to type the label.

An IF statement would be something like: =IF(Qnum ='BL5.1',Subtext,null())

Qlik Sense likes that expression, but returns "-" in the legend. So it's not evaluating it correctly.  I don't know how to write the expression to get the desired result.

Thanks

[wttaryde · Accepted solution]

Found the solution on another post:

=Aggr([Subtext Alias (row)],Qnum='BL5.1')