PointInPolygon {wflo}

Checks whether a point is inside a polygon.

Description

Uses the famous Jensen test to check whether a provided point is inside a polygon, the latter defined by a set of points.

Usage

PointInPolygon(PointMat, TestPoint)

Arguments

PointMat

a 2 x 4 matrix, four corner points of each x and y coordinates.

TestPoint

a vector of two containing x and y coordinates of a point to test.

Value

PointInPolygon returns TRUE if the point is inside the polygon, or FALSE, else.

Author(s)

Carsten Croonenbroeck

References

Jensen, N. O. (1983). A note on wind generator interaction. Roskilde: Risø National Laboratory. Risø-M, No. 2411

See Also

JensenTrapezoid to compute a Jensen trapezoid.

Examples

set.seed(1357)
Angle <- runif(n = 1, min = 0, max = 360)
Point <- runif(n = 2, min = 0, max = 1)
Dist <- rnorm(n = 1, mean = 200, sd = 200)

MyTrapezoid <- JensenTrapezoid(Angle, Point, Dist)

plot(x = MyTrapezoid[1, ], y = MyTrapezoid[2, ], xlab = "", ylab = "")
lines(x = c(MyTrapezoid[1, 1], MyTrapezoid[1, 2]), y = c(MyTrapezoid[2, 1], MyTrapezoid[2, 2]))
lines(x = c(MyTrapezoid[1, 2], MyTrapezoid[1, 3]), y = c(MyTrapezoid[2, 2], MyTrapezoid[2, 3]))
lines(x = c(MyTrapezoid[1, 3], MyTrapezoid[1, 4]), y = c(MyTrapezoid[2, 3], MyTrapezoid[2, 4]))
lines(x = c(MyTrapezoid[1, 4], MyTrapezoid[1, 1]), y = c(MyTrapezoid[2, 4], MyTrapezoid[2, 1]))

NumTest <- 50

xTest <- runif(n = NumTest, min = min(MyTrapezoid[1, ]), max = max(MyTrapezoid[1, ]))
yTest <- runif(n = NumTest, min = min(MyTrapezoid[2, ]), max = max(MyTrapezoid[2, ]))

for (i in 1:NumTest)
{
	ThisPoint <- c(xTest[i], yTest[i])
	if (PointInPolygon(MyTrapezoid, ThisPoint))
	{
		points(ThisPoint[1], ThisPoint[2], pch = 16, col = "green")
	} else
	{
		points(ThisPoint[1], ThisPoint[2], pch = 16, col = "red")
	}
}