MiRData contains files needed for miRComb package (http://mircomb.sourceforge.net)
There are two ways of installing miRData from GitHub:
Use devtools package:
library(devtools)
install_github("mariavica/miRData", ref="master", build_vignettes = TRUE)
Or with githubinstall package:
library(githubinstall)
gh_install_packages("miRData", ref = "master", build_vignettes = TRUE)
MiRComb and miRData code is stored at GitHub: https://github.com/mariavica/mircomb; https://github.com/mariavica/mirdata.
In the Session Info section of the Vignette (http://mircomb.sourceforge.net/documentation.html) you can check the exact versions of the packages used on the last version. If you are a GitHub user, you can fork the repository and make changes on a separate branch. These changes can be later incorporated to the main repository with a pull request.
Basic guide to GitHub users: https://guides.github.com/activities/hello-world/.
package.skeleton() function will help you to create any *Rda and *Rd file.
https://www.r-bloggers.com/building-packages-in-r-part-1-the-skeleton/
https://cran.r-project.org/doc/contrib/Leisch-CreatingPackages.pdf
For saving Rda files exclusively, you can also use save() function (https://thepracticalr.wordpress.com/2017/04/27/load-save-and-rda-files/)
See also one example of *Rda file creation in: https://github.com/mariavica/mirdata/tree/master/misc