Contribution graphs > Rest should be split into positive and negative sections

[marc-vdm]

Currently in contribution graphs, AB shows a rest containing a remainder of processes. While this is great, the rest is an aggregate of potentially hundreds or thousands of processes when using common background databases like ecoinvent. Among this 'rest' section, some number of processes will have a negative impact instead of a positive one, though often, the sum of 'rest' will be positive (though lower, as these negative numbers would also be counted, lowering the total sum).

It may be better to split rest up based on the sign of the processes (should be easy in pandas with just a score > 0 selection). This way, AB can show that the remainder has both a positive and a negative impact, which would be more realistic.

Figure below is an example of such a case. I know that in this system there are negative flows for one of the reference flows, but this representation of the contributions only shows a positive 'rest'.

For implementation, I think we could keep the same color for both 'rest' flows, just rename them to rest (positive) and rest (negative).

Related issues: #647, #782, #635.

Good place to start is here:

activity-browser/activity_browser/bwutils/multilca.py

Line 397 in 1715a17

('Rest', ''): C[col, :].sum() - top_contribution[:, 0].sum(),