Uses a discrete version of Green's Theorem to calculate the area of a
polygon.
USAGE:
poly.area(x, y)
REQUIRED ARGUMENTS:
x
a list with components named
"x" and
"y",
a 2-column matrix, or a vector containing
the horizontal coordinates of the vertices that form the polygon of interest.
OPTIONAL ARGUMENTS:
y
if x is a vector of X-coordinates then this must contain the corresponding
vertical or Y-coordinates.
VALUE:
a double precision number representing the area enclosed by the polygon
with vertices defined by
x and
y
SEE ALSO:
,
EXAMPLES:
lansing.chull <- lansing[chull(lansing),]
poly.area(lansing.chull) # This should be close to unity.