Determine Whether Polygons are Convex

Description

Determines whether polygons found in a PolySet are convex.

Usage

isConvex (polys)

Arguments

Details

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.

Value

PolyData with columns PID, SID (may be missing), and convex. Column convex contains Boolean values.

See Also

isIntersecting, PolySet.

Examples

#--- load the data (if using R)
if (!is.null(version$language) && (version$language == "R"))
  data(nepacLL);
#--- calculate then print the polygons that are convex
p <- isConvex(nepacLL);
#--- nepacLL actually contains no convex polygons
print(p[p$convex, ]);