Add example of visualizing PropertyLayers to example models

[EwoutH]

Currently none of the Example models visualize the PropertyLayers, it would be useful if at least one of them did. This could be Sugarscape Constant Growback Model with Traders for example.

See:

• bug fixes for draw_property_layers #2548

[quaquel]

I looked at the sugarscape example, and the current portrayal of property layers is not compatible with what would be required for sugarscape. The issue is that currently the entire layer is shown, and you cannot mask part of the layer as done in sugarscape.

[EwoutH]

Can you set alpha to 0 for certain values you want to hide?

[quaquel]

alpha is applied to the entire layer

[EwoutH]

It seems I did allow scaling over alpha instead of color in the implementation (#2336): 7c8e98b

Any matplotlib color is valid. The highest value will have that color with 0% opacity, the lowest with 100% opacity (which can again be scaled with modifying vmin and vmax).

That should work if you define a "color" instead of a "colormap" in the propertylayer_portrayal dict.