I am classifying an .adf wind resource map which I vectorised using the Polygonise tool (which worked very well). I have classified the data using the Graduated symbol renderer using Natural Breaks (Jenks) mode. Unfortunately although the Range column will take decimals, only columns with whole numbers will render. Does anyone know if there is a way to do this. Am using QGIS 1.7.3.
Interesting. This looks like a bug. I can replicate your problem using the
Investigating a bit further reveals the automatic ranges are floating point numbers with exponents, e.g.
On windows 7 this can be done with the built in Calculator program. Just fire it up, set View to Scientific, enter a decimal and than tap the [Exp] button.
To convert in python, try this:
My error, I used the Classify button all along. The problem seems to be that the converted column, DN, has a precision level of 1 whereas I need something like ±0.2.