Can TERGM be used to fit bunch of networks files from 1.net to n.net?

Question

Can TERGM be used to fit bunch of networks files from 1.net to n.net? With each file, the number of nodes and vertices increases. I have

For example, when we fit a particular network (suppose 6.net), we run the following after preprocessing the network (i.e finding the metrics value and adding the metrics to the nodes)

network_fit<-ergm(my_network~edges+nodecov("degree")+nodecov("betweenness")+nodecov("closeness")+nodecov("pagerank")+nodecov("eigen_c")+nodecov("clustcoeff"))

Can the same be done using TERGM?

I have fit the network using TERGM over 49 networks (1.net to 48.net) fit <- tergm(net_y.dyn~edges + nodematch("degree"), estimate = 'CMLE', times = c(0:48))

I am getting the following warning

Starting maximum pseudolikelihood estimation (MPLE):
Evaluating the predictor and response matrix.
Maximizing the pseudolikelihood.
Finished MPLE.
Stopping at the initial estimate.
Evaluating log-likelihood at the estimate. 
Warning message:
In NetSeries(nw, times, NA.impute = control$CMLE.NA.impute) :
  Active vertex set varies from time point to time point. Estimation may not work.

Can anyone explain why this warning is showing?

Answer 1

TERGM assumes the nodeset is fixed. The warning is because you are submitting a series of networks of different sizes.

Having said that, it is possible to incorporate exogenous node entry and exit processes into a TERGM -- such specifications are used in EpiModel framework, an example can be found here https://github.com/EpiModel/EpiModel-Gallery/tree/main/2018-08-SIwithVitalDynamics. A more general model with endogeneous node entry and exit is a subject of ongoing research.