MASTER_SITES is defined in math/R/Makefile.extension, which should be
included by all R packages. Therefore, MASTER_SITES should not normally
be defined in the Makefile for an R package.
R port of Angus Johnson's open source library Clipper. Performs
polygon clipping operations (intersection, union, set minus, set
difference) for polygonal regions of arbitrary complexity, including
holes. Computes offset polygons (spatial buffer zones, morphological
dilations, Minkowski dilations) for polygonal regions and polygonal
lines. Computes Minkowski Sum of general polygons. There is a function
for removing self-intersections from polygon data.
