Signed Area of Polygon
Calculate the area of a polygon and its boundary direction.
matrix containing the
x,y-coordinates of the vertices of the polygon boundary.
positive numeric, the area of the polygon.
integer, 1 if the polygon orientation is anticlockwise, -1 otherwise.
copy of the passed argument
This function is provided here so that users do not need to load other packages, as it is not available in the base R packages.
Joseph O'Rourke, Computational Geometry in C (2nd Edition), Cambridge University Press, 2000 edition.