This is a demo of the {quadrangle} package.
See demo.R (at the console) and app.R (Shiny).
This is an R package. If you wanted, you could install it using dev_tools::install_github.
If you (i.e. future me) need to deploy it from scratch, there is a missing file
from this repository, secret.txt, which contains the ID (as a bare string)
of a Google Drive folder that contains some images for the demo.R script.