Nodes are universities around the world. I'm doing ERGM (Exponential random graph models) using R about what factors affect universities to have collaborations. I have node attribute including both longitude and latitude information. I would like to use the information of geo-locations to test if the distance between universities (nodes) will affect the probability of collaboration. I am aware that I should make new ERGM terms, but I don't have a clue of doing.
The starting code is something like the following:
library(statnet)
model<-ergm(g ~ edges + gwesp(0.2, fixed=T),
control=control.ergm(parallel=np, parallel.type="PSOCK"))