icosa (originally εἴκοσι for twenty) refers to the icosahedron, the platonic solid with the highest number of faces. The ‘icosa’ extension is an implementation of icosahedral grids in three dimensions. The spherical-triangular tessellation can be set to create grids with custom resolutions. Both the primary triangular and their inverted penta-hexagonal grids can be calculated. Additional functions are provided that allow plotting of the grids and associated data, the interaction of the grids with other raster and vector objects, and treating the grids as a graphs.
These grids are often called icospheres, and have an important use in material design, architecture, computer graphics and chemistry.
Implementations of similar grids are available in R with the H3 library (h3-js) and the ddgridR libraries. These other implementations are based on hierarchical organizations of grid cells, which allows very high-resolution. In contrast, the icosa package was optimized for coarser resolutions, providing a more gradual change of cells sizes, 3D-based operations (e.g. grid rotation), and to be used in the R environment for spatially isotropic analysis - especially when it comes to latitudinal patterns. It also allows access to not only hexagonal, but triangular grids as well.
- Finishing vignettes in Tutorials
- Paper about the package (long overdue)
- Moving internal vector-representation from