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Re: [igraph] network layout 'grouping' by vertex attribute

From: Bob Pap
Subject: Re: [igraph] network layout 'grouping' by vertex attribute
Date: Sat, 31 Aug 2013 12:57:40 +0200

I will give it a try, this sounds like a sensible suggestion, although - for the first suggestion - my network already has weights (the strength of a relationship). Need to find out how to create (how does one assign coordinates and create noise?) and assign (how does one 'place a node'?). Have some work with layouts to do. Many thanks.

Bob Pap

On 29 August 2013 12:22, Tamás Nepusz <address@hidden> wrote:
> Maybe some has faced the following situation: vertices in a  network have an attribute (think of - for example - a sport they play frequently), which has a role in how they are related (within-attribute edges are more frequent and stronger than outside-attribute).  Would it be possible to layout the network in a way that graphically 'groups' the attributes (sport teams) and then still shows the vertices and their edges in a sensible way?
You can probably use the weighted Fruchterman-Reingold layout in igraph. Set up the edge weights such that edges within a group have significantly larger weight than edges between groups, and then run the layout algorithm. That should do the trick. In case the layout algorithm is not able to figure out an appropriate layout on its own, you can "help" it by providing it with a seed layout where the nodes in the different groups are already separated to some extent. For instance, if you have k groups, then choose k points along the circumference of a circle with a sufficiently large radius, and place the nodes in group i around point i, adding some random noise to avoid nodes ending up at exactly the same position. Then pass this seed layout to the weighted Fruchterman-Reingold layout with appropriate weights.

All the best,

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