R Grid Coordinates

Cited from grid Graphics

Each viewport has a number of coordinate systems available. There are four main types: absolute coordinates (e.g.,"inches", "cm") allow locations and sizes in terms of physical coordinates -- there is no dependence on the size of the page; normalised coordinates (e.g., "npc") allow locations and sizes as a proportion of the page size (or the current viewport); relative coordinates (i.e.,"native") allow locations and sizes relative to a user-de ned set of x- and y-ranges; referential coordinates (e.g., "strwidth") where locations and sizes are based on the size of some other graphical object.