create point vector layer with continuous-valued labels

[Andreas Janz]

• sample some points from fraction_polygons_l3.tif testdata in all 6 classes; try to cover the full range of fractions from 0 to 1 for each class

  will be single-part, so we can close #392

‌

[Andreas Janz]

Sampled all data:

‌

It is proposed to select one sample per class per bin, with bin edges at [0, 10, 20, …, 90, 100] percent.

Results in 60 samples overall.

[Andreas Janz]

Done. And also found the Diagram-Renderer to be very useful for styling.

‌