tests/testthat/test-offsets.R

In ergm: Fit, Simulate and Diagnose Exponential-Family Models for Networks

#  File tests/testthat/test-offsets.R in package ergm, part of the Statnet
#  suite of packages for network analysis, https://statnet.org .
#
#  This software is distributed under the GPL-3 license.  It is free, open
#  source, and has the attribution requirements (GPL Section 7) at
#  https://statnet.org/attribution .
#
#  Copyright 2003-2025 Statnet Commons
################################################################################
o <- options(ergm.eval.loglik=TRUE)

set.seed(0)

data(sampson)
total.theta <- coef(ergm(samplike~edges))
offset.theta <- pi

test_that("Linear ERGM with free parameter before offset", {
  e1 <- ergm(samplike~edges+offset(edges), offset.coef=c(pi))
  expect_equal(coef(e1)[1], total.theta-offset.theta, tolerance=0.00001, ignore_attr=TRUE)
  expect_equal(attr(logLik(e1),"df"),1)
})

test_that("Linear ERGM with free parameter after offset", {
  e2 <- ergm(samplike~offset(edges)+edges, offset.coef=c(pi))
  expect_equal(coef(e2)[2], total.theta-offset.theta, tolerance=0.00001, ignore_attr=TRUE)
  expect_equal(attr(logLik(e2),"df"),1)
})

test_that("Linear ERGM with partial offsets", {
  e3 <- ergm(samplike~edges+nodematch("group", diff=TRUE, levels=-2))
  e3a <- ergm(samplike~edges+offset(nodematch("group", diff=TRUE), 2), offset.coef=0)
  e3b <- ergm(samplike~edges+offset(nodematch("group", diff=TRUE), c(FALSE,TRUE,FALSE)), offset.coef=0)
  expect_equal(coef(e3a)[-3], coef(e3), tolerance=0.00001)
  expect_equal(coef(e3b)[-3], coef(e3), tolerance=0.00001)
  expect_equal(logLik(e3a), logLik(e3), tolerance=0.00001)
  expect_equal(logLik(e3b), logLik(e3), tolerance=0.00001)
})

test_that("Curved ERGM with partial offsets", {
  e4 <- ergm(samplike~edges+gwesp(0.25, fix=TRUE), control=control.ergm(seed=0,MCMLE.maxit=2))
  e4a <- ergm(samplike~edges+offset(gwesp(),c(FALSE,TRUE)), offset.coef=0.25, control=control.ergm(seed=0,MCMLE.maxit=2))
  expect_within_mc_err2(e4a, e4, -3, TRUE)
  expect_equal(logLik(e4a), logLik(e4), tolerance=0.01, ignore_attr=TRUE)
})


options(o)