improve sankey diagram

[arnaudon]

the sankey diagram ploting function works but is rudimentary. Some work to improve it is needed

[arnaudon]

rough version added, some work to improve

[arnaudon]

should move it to contrib folder

[arnaudon]

moved to contrib folder

[juni-schindler]

Do we need to improve the Sankey diagrams further?

[juni-schindler]

I have a local version that adds colour to the flow arrows in the Sankey diagram. Should I make a new PR for that?

[arnaudon]

sure, go ahead!

[juni-schindler]

It would be good to have the option to include labels for Markov scale (x-axis) and community indices in the plot.

[juni-schindler]

For a different project, I developed code to plot the Sankey diagram with an optimised layout: https://github.com/barahona-research-group/MCF/blob/main/mcf/sankey.py

The layout optimisation uses my fork of the code of this paper: https://www.biorxiv.org/content/10.1101/2025.06.13.659656v1

For a multiscale SBM the original Plotly layout looked like this (random color assignment):

The layout optimisation leads to a much nicer figure where the structure is already apparent in black and white (ground truth shades added manually):

If you like we could try to integrate this Sankey diagram plotting code here, too, @arnaudon .

But it would be nice to additionally have a good way of assigning colours.