I'm a totally beginner with QGIS and maybe I have a very easy problem, but I can't help myself. I got an elevation shapefile with classes of elevations like that: 1-100m, 101-200m, ... When I try to classify this dates to display them with a continuous shift of colours, QGIS always sorts the classes like that: 1-100m, 1001-1101m, 101-200m, 1101-1200m, ... So the colours of the elevation classes are mixed and don't display the continuous shift. Is there an easy way to sort the classes in the attribut table in the right way? Thanks a lot!