[statnet_help] Specifying TERGM constraint on bipartite network

[Terin Mayer]

Hello Statnet Community—

Greetings, and with much appreciation for all your work on this incredible collection of open-source resources! 

I am writing to request information and advice for estimating a TERGM on a bipartite network with a dyad-independent constraint on the sample space. 

I am attempting to fit a TERGM to a bipartite network of local units of government participating in watershed management organizations. I observe this network over a several decade time-span. During that range, some watershed management organizations (mode 2 nodes) are created and some disband. There are geographic constraints on the possible links, which I have represented as an edge-list and passed to the "fixallbut()” constraint operator.  

I am encountering some difficulties in getting the model to run. In certain circumstances initial MPLE estimation doesn’t complete (“Error in set.constr.type(lprec, rep(“>=“, NROW(X.bar))): ’types’ and ‘constraints’ are not the same length.) In other attempts, the MPLE estimation appears to get stuck on “evaluating the predictor and response matrix". In all cases, I get the warning “Active vertex set varies from time point to time point. Estimation may not work.” 

Being new at this, I’m having some difficulty discerning when I should keep debugging vs. when I need to reconceptualize my data to fit existing package limitations. 

Specifically, my questions are:
- Should I anticipate that fixing the vertex set will improve my chances of successful modeling? (i.e. not representing creation/destruction of the second mode in the bipartite scheme and thus not having changes in the active vertex set)
- What is the correct way to specify the “fixallbut(free.dyads)” constraint with a bipartite network? Is there a way of using permanent ids to ensure that the edgelist (which I build using node names) correctly picks out the vertexes in each network panel? 

I have refrained from providing a reproducible example, but would readily do so if that would help clarify my query. 

Thanks kindly for any help you can provide!
Terin

Terin Mayer
PhD Candidate in Public Affairs, University of Minnesota
UC Berkeley MPP ’18 
terin.mayer at gmail.com 
terin at umn.edu <mailto:terin at umn.edu> | 612-812-0710
terinvmayer.com <http://terinvmayer.com/> 




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