I have a health data set and an "urban stress". I'm trying to do bivariate analysis within QGIS using Joshua Stevens lessons at http://www.joshuastevens.net/cartography/make-a-bivariate-choropleth-map/. As per Joshua's instructions, in QGIS the best way to do this is to write a CASE function to classify values into a preset organizational value. For example:
CASE WHEN "CrimeRate" > 4.0 THEN 3 WHEN "CrimeRate" <= 4.0 AND "CrimeRate" > 2.0 THEN 2 ELSE 1 END
This field calculator function worked perfectly. The next example filled my column with NULL values:
CASE WHEN "POOR345" > 52.9 THEN 'C' WHEN "POOR345" <= 52.9 AND "POOR345" > 40.3 THEN 'B' ELSE 'A' END
Does anyone have an idea of why this is happening?