Add more datasets

[chrismainey]

To add more datasets, you can use this issue.
Please make sure that all pull requests:

• contain a dataset in .RData format
• contain a shell function with roxygen comments for a help file
• add, or have plans to add, a vignette showing use of the data

[emmavestesson]

It is usually better to use .rds files. That way the user can read in the object (data set) and give it a name and you don't risk overwriting someone else's data.

[chrismainey]

.Rdata is (as far as I know) the format that the 'data' argument picks up, like 'data(mtcars)'. RDS is a better format, and I'd prefer to use that, but the R data package mechanisms aren't set to deal with this yet, and I suspect it wouldn't build or pass CRAN checks.