I am doing a lab worksheet and I am having a hard time figuring out what to put in in the expression box.
GENERAL STEP: You need to identify Aspen and Birch (Select by Expression) and export these stands to a separate shapefile, naming it something like AspenBirch.shp. Then open the AspenBirch attribute table and alternately select the young, intermediate, or old tree stands, exporting each to create three new shapefiles.
Out of the 506 Vegetation records, 111 are Aspen or Birch. Of these:
- 30 records are Young; less than 18 year, from 2006 through 1988
- 25 records are Intermediate; between 19-34 years, from 1987 through 1972
- 30 records are Old; 34 years and over, from 1971 to 1888.
Below is the attribute table data that the records are in. I am a beginner QGIS user so I am still learning how to come up with the correct valid expressions.
UPDATE: I have entered in the adjusted expression in the field calculator like in the answer reply but under my Category all it shows is NULL values. I may have made a small mistake but I can't tell since the expression doesn't show anything invalid.