参考文献
Grolemund, Garrett. 2014. Hands-on Programming with r. 1 edition. Houston: O’Reilly Media. https://rstudio-education.github.io/hopr/.
Grolemund, Garrett, and Hadley Wickham. 2017. R for Data Science: Import, Tidy, Transform, Visualize, and Model Data. 1 edition. Houston: O’Reilly Media. http://r4ds.had.co.nz/.