Determine Whether Polygons are Convex
Determine whether polygons found in a PolySet are convex.
isConvex (polys)
polys |
PolySet to use. |
Convex polygons do not self-intersect. In a convex polygon, only the first and last vertices may share the same coordinates (i.e., the polygons are optionally closed).
The function does not give special consideration to holes. It returns
a value for each unique (PID, SID), regardless of
whether a contour represents a hole.
PolyData with columns PID, SID (may be missing),
and convex. Column convex contains Boolean values.
Nicholas M. Boers, Associate Professor – Computer Science
MacEwan University, Edmonton AB
Last modified Rd: 2013-04-10
local(envir=.PBSmapEnv,expr={
#--- load the data (if using R)
if (!is.null(version$language) && (version$language=="R"))
data(nepacLL,envir=.PBSmapEnv)
#--- calculate then print the polygons that are convex
p <- isConvex(nepacLL);
#--- nepacLL actually contains no convex polygons
print(p[p$convex,])
})Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.