Plotting: multiple self-loops on a vertex are plotted on top of each other

[szhorvat]

When a vertex has multiple self-loops, they are plotted on top of each other. The graphs 0-0 and 0-0, 0-0 are not visually distinguishable when plotted.

These two graphs look the same:

plot(Graph([(0,0),(0,0)]))
plot(Graph([(0,0)]))

Related: https://github.com/igraph/rigraph/issues/407

[szhorvat]

I realize this is not easy. For some inspiration, Mathematica visualizes these like this:

As you can see, a nice solution will consider not only other self loops, but also the position of other non-loop edges.

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[iosonofabio]

Is this still present in the matplotlib interface?

[ntamas]

The Matplotlib backend seems to be better in handling multiple self-loops; just tested this now in Google Colab.

[szhorvat]

Is this still present in the matplotlib interface?

Yes, here's an example:

ig.plot(ig.Graph.Formula('a-b-c-c-c-c-a-b', simplify=False))

[iosonofabio]

Is this the develop branch? If not please test with that

[szhorvat]

Yes, it is with the latest develop branch.

Should this work? I vaguely remembered that you fixed this, so I was actually surprised to see that it didn't work.

[szhorvat]

@iosonofabio I remembered correctly, you did fix it. It works in the released version, but it does not work on develop. Here's what I get with 0.9.8:

ig.plot(ig.Graph.Formula('a-b-c-c-c-c-a-b', simplify=False), target=plt.axes())