@techreport{murrell-groups-2021,
  title="Groups, Compositing Operators, and Affine Transformations in R Graphics",
  author = {Paul Murrell},
  year={2021},
  note={version 3},
  institution={Department of Statistics, The University of Auckland},
  number={2021-02},
  url={https://stattech.blogs.auckland.ac.nz/2021/11/15/2021-02-groups-compositing-operators-and-affine-transformations-in-r-graphics},
  doi={http://dx.doi.org/10.17608/k6.auckland.17009120}
}