tests/testthat/test-offset_zeroinfl.R

In javifar/ggeffects: Create Tidy Data Frames of Marginal Effects for 'ggplot' from Model Outputs

if (suppressWarnings(
  require("testthat") &&
  require("ggeffects") &&
  require("pscl") &&
  getRversion() > "3.5")) {
  #Generate some zero-inflated data
  set.seed(123)
  N <- 100 #Samples
  x <- runif(N, 0, 10) #Predictor
  off <- rgamma(N, 3, 2) #Offset variable
  yhat <- -1 + x * 0.5 + log(off) #Prediction on log scale
  dat <- data.frame(y = NA, x, logOff = log(off)) #Storage dataframe

  dat$y <- rpois(N, exp(yhat)) #Poisson process
  dat$y <- ifelse(rbinom(N, 1, 0.3), 0, dat$y) #Zero-inflation process

  #Fit zeroinfl model using 2 methods of offset input
  m1 <- zeroinfl(y ~ offset(logOff) + x | 1, data = dat, dist = "poisson")
  m2 <- zeroinfl(y ~ x | 1,
                 data = dat,
                 offset = logOff,
                 dist = "poisson")

  #Fit zeroinfl model without offset data
  m3 <- zeroinfl(y ~ x | 1, data = dat, dist = "poisson")

  test_that("offset-zeroinfl-1", {
    pr <- ggpredict(m1, "x")
    expect_equal(ncol(pr), 6)
    expect_equal(
      colnames(pr),
      c("x", "predicted", "std.error", "conf.low", "conf.high", "group")
    )
    expect_equal(
      pr$conf.low,
      c(0.38151, 0.64241, 1.08141, 1.81951, 3.05894, 5.1351, 8.59457,
        14.28775, 23.41852, 37.68751, 59.9237),
      tolerance = 1e-3
    )
  })

  if (utils::packageVersion("insight") > "0.10.0") {
    test_that("offset-zeroinfl-2", {
      pr <- ggpredict(m2, "x")
      expect_equal(ncol(pr), 6)
      expect_equal(
        colnames(pr),
        c("x", "predicted", "std.error", "conf.low", "conf.high", "group")
      )
      expect_equal(
        pr$conf.low,
        c(0.38151, 0.64241, 1.08141, 1.81951, 3.05894, 5.1351, 8.59457,
          14.28775, 23.41852, 37.68751, 59.9237),
        tolerance = 1e-3
      )
    })
  }

  test_that("offset-zeroinfl-3", {
    pr <- ggpredict(m3, "x")
    expect_equal(ncol(pr), 6)
    expect_equal(
      colnames(pr),
      c("x", "predicted", "std.error", "conf.low", "conf.high", "group")
    )
    expect_equal(
      pr$conf.low,
      c(0.76538, 1.21064, 1.91433, 3.02552, 4.77779, 7.53369, 11.84387,
        18.49956, 28.52172, 43.24606, 64.8289),
      tolerance = 1e-3
    )
  })
}