Assortativity measures and others about squidpy HOT 5 CLOSED

Another one could be the Ripley's K value, see these papers:
https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1003808
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0080914

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Couple notebooks to evaluate ripley values over coordinates or graph in #19

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Potentially interesting: https://nbviewer.jupyter.org/github/pysal/pointpats/blob/master/notebooks/Quadrat_statistics.ipynb

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@AnnaChristina , @ilibarra wrote this on MM:
related to the assortativity metric:

CellOracle computes two metrics: within module degree (z) and participation coefficient (P). Maybe worth take a look if this is useful on top or instead of assort.
They do this for each cluster or cluster pair, so you would have a point in the (x, y) space based on that.
https://www.biorxiv.org/content/10.1101/2020.02.17.947416v3.full

Maybe interesting to look into that? Not sure really

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@AnnaChristina Malte just posted this on MM:
Also: various network summary statistics used to identify node roles:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103733

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