Reading and writing of "ESRI shapefile" format spatial data. Only the three vector types (points, lines, and polygons) can be stored in shapefiles.
These are simple wrapper functions around readOGR and writeOGR (rgdal package).
A shapefile should consist of at least four files: .shp (the geometry), .dbf (the attributes), .shx (the index that links the two, and .prj (the coordinate reference system). If the .prj file is missing, a warning is given. If any other file is missing an error occurs (although one could in principle recover the .shx from the .shp file). Additional files are ignored.