I had various layers and through geoprocessing tools "Clip" and "Difference" I have created one layer in QGIS 2.16. This layer has 98 attributes - polygons. I want to calculate the area of each of the polygons and only retain those that are larger than 10ha:
Open Attribute table -> toggle edit -> Add field -> Name = "Area" (real).
I do obtain the calculated area for the first 38 polygons, but not for the remaining ones. I tried to locate the ones without calculated area and obtain this error:
What does this error mean?
Is it even possible to calculate the area for the remaining ones? If so, How?