Package where to store data. Defaults to package in working
directory.
internal
If FALSE, saves each object in individual
.rda files in the data/ directory. These are available
whenever the package is loaded. If TRUE, stores all objects in
a single R/sysdata.rda file. These objects are only available
within the package.
overwrite
By default, use_data will not overwrite existing
files. If you really want to do so, set this to TRUE.
compress
Choose the type of compression used by save.
Should be one of "gzip", "bzip2" or "xz".