[statnet_help] Modeling group formation with ERGMs

Flavien Ganter fg2465 at columbia.edu
Wed Aug 19 09:55:09 PDT 2020

Hi all,

I am working on data from a series of experiments in which participants
cluster into groups of participants. All participants should be in one, and
only one, group; a group is formed by at least two participants, and the
overall number of groups that participant can form is bounded ([4;12]). I'm
interested in studying homophily in the group formation process.

I wanted to model this data with a series of ERGMs (one per experiment), by
considering edges as representations of group membership; that is,
participants in the same group would all be tied to each other, and
participants in different groups would never be tied to each other.
So, I would like to specify an ERGM with two constraints:

1. Each node has to be in one, and only one, complete and isolated
community, that is, tied with every other node of the community, and not
tied with every other node that is not in the community. My understanding
is that it would be equivalent to constraining simulated networks to not
have any stars / open triads—if there is an indirect path between two
nodes, there has to be an edge between these two nodes that closes the
2. The number of groups is between 4 and 12.

And I would have homophily terms, and a term for the actual number of

Including the homophily terms is straightforward, but I could not find how
to implement both constraints and the term for the total number of working
groups. Can you see a way to implement these things with statnet::ergm? Or
with any other program you can think of? If not, I'd be curious if anyone
has ideas on how to deal with this data structure in a different way.

Thanks so much in advance for your insights,


*Flavien Ganter*PhD Student & Paul F. Lazarsfeld Fellow
Department of Sociology | Columbia University
501 Knox Hall, 606 West 122nd Street, New York, NY 10027
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