ggplot2 (>= 2.1.0), tidyr (>= 1.0.2), dplyr (>= 0.4.3),
data.table, cowplot, crayon, gtable, methods, plyr, purrr,
readxl, tibble, haven, stringr, httr, ggpubr
testthat, covr, devtools, roxygen2, knitr, rmarkdown