triangulate {ads} | R Documentation |
Function triangulate
decomposes a simple polygon (optionally having holes) into contiguous triangles.
triangulate(outer.poly) triangulate(outer.poly, holes)
outer.poly |
a list with two component vectors x and y giving vertice coordinates of the polygon
or a vector (xmin,ymin,xmax,ymax) giving coordinates (ximn,ymin) and (xmax,ymax) of the origin and the
opposite corner of a rectangle sampling window (see swin ). |
holes |
(optional) a list (or a list of list) with two component vectors x and y giving vertices
coordinates of inner polygon(s) delineating hole(s) within the outer.poly . |
In argument outer.poly
, the vertices must be listed following boundary of the polygon without any repetition (i.e. do not repeat the first vertex).
Argument holes
may be a list of vertices coordinates of a single hole (i.e. with x and y component vectors) or a list of list for multiple holes,
where each holes[[i]]
is a list with x and y component vectors. Holes' vertices must all be inside the outer.poly
boundary (vertices on the boundary
are considered outside). Multiple holes do not overlap each others.
A list of 6 variables, suitable for using in swin
and spp
, and giving the vertices coordinates (ax,ay,bx,by,cx,cy) of the triangles that
pave the polygon. For a polygon with t holes totalling n vertices (outer contour + holes), the number of triangles produced
is (n-2)+2t, with n<200 in this version of the program.
Goreaud, F. and Pélissier, R. 1999. On explicit formula of edge effect correction for Ripley's K-function. Journal of Vegetation Science, 10:433-438.
Narkhede, A. & Manocha, D. 1995. Fast polygon triangulation based on Seidel's algoritm. Pp 394-397 In A.W. Paeth (Ed.)
Graphics Gems V. Academic Press. http://www.cs.unc.edu/~dm/CODE/GEM/chapter.html.
data(BPoirier) BP<-BPoirier plot(BP$poly1$x,BP$poly1$y) # a single polygon triangulation tri1<-triangulate(BP$poly1) plot(swin(BP$rect,tri1)) # a single polygon with a hole tri2<-triangulate(c(-10,-10,120,100),BP$poly1) plot(swin(c(-10,-10,120,100),tri2))