## ----include = FALSE----------------------------------------------------------
NOT_CRAN <- identical(tolower(Sys.getenv("NOT_CRAN")), "true")
eval_packages <- requireNamespace(c("kableExtra", "ggplot2"))
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>",
  purl = NOT_CRAN,
  eval = NOT_CRAN && eval_packages
)