add graph viz section

[mdeff]

As discussed in #58, I'm adding a graph visualization section with 13 tools. I've tried to order by popularity, but I don't have access to monthly download counts. Feel free to add, remove, or reorder them.

[ceball]

This is quite a challenge to do, but will be very helpful :) I've been quite familiar with various of these libraries from time to time over the years, but now I basically can't remember which is which or which one I should use for what! And I have never heard of some of the ones you've listed, so I'll have to check them out.

A few miscellaneous thoughts (not requests or even suggestions to follow up on):

• Could the tools be grouped in some way(s)? E.g. some only work in jupyter lab, some are based on graphviz, etc. Not sure grouping would be helpful. Maybe I mean tagged in some way. Not really sure, just pointing out there are ways to distinguish or group them I guess.
• These are not the only tools that can be used to visualize graphs from python :)
  • E.g. holoviews has support for graphs (e.g. http://holoviews.org/user_guide/Network_Graphs.html) - and so do I guess most of the already listed tools...
  • There are still more graphviz wrappers in one form or another, e.g. "pydot". I don't know if they are active and can't remember if I've used them.
  • shameless plug for a colleague's new tool: https://github.com/timkpaine/ipydagred3 :)

[mdeff]

Yeah the plethora of tools is confusing to me too. Especially as they tend to be experiments that finally die out.

Tags would be great. They could be based on usage, technology, or "access" (e.g., graphistry requires a server with an API key). There's some discussion about tags / groups in #7.

You're right there are other tools. I've added those I knew plus some I found by searching. ;) Regarding your specific suggestions:

• I didn't know holoviews could do that. Most generic viz tools can do it with a scatter plot and a set of lines. Should we mention that in the section intro text?
• I saw pydot, but it didn't seem to be for viz especially. I discarded it for the same reason I discarded networkit and snap. But I'm ok with adding it if you think it's a reasonable tool for viz (I've never used it).
• Dagre is great! Let's add https://github.com/timkpaine/ipydagred3, even if it seems to be in quite an early stage for now. ;) It'll go well with ipysigma (same goal and state). Looking forward to them growing!

[jbednar]

From https://pythonhaven.wordpress.com/2009/12/09/generating_graphs_with_pydot/ , it looks like pydot can be thought of as a graph visualization tool, so I've added it. I've also added builton info for the ones I know about ; other info can be added in a followon PR if anyone has more to put in.

[mdeff]

Thanks for reviewing and merging! Agreed with all your comments and changes.

[mdeff]

Latest discovery: https://github.com/QuantStack/ipycytoscape

[jbednar]

PR?

[mdeff]

#64 ;)