ellipse, graphics, grDevices, grid, lattice, stats
gridBase, knitr, Matrix, rmarkdown, testthat
gridBase, knitr, Matrix, psych, rmarkdown, sfsmisc, testthat
gridBase, knitr, Matrix, psych, rmarkdown, seriation,
sfsmisc, testthat
gridBase, hexbin, knitr, MASS, Matrix, psych, rmarkdown,
seriation, sfsmisc, testthat