Circular or directional statistics (see also wikipedia) is the subfield of statistics that deals with the analysis of directions, often angles. A typical example of such a question is the mean of an angular quantity (see wikipedia).
Unfortunately, analysis options for circular data in R are limited. The following links may be a good start
- https://cran.r-project.org/web/packages/circular/index.html
- http://stats.stackexchange.com/questions/tagged/circular-statistics
- Book: Circular Statistics in R, http://circstatinr.st-andrews.ac.uk/