pracma (version 1.4.5)

inpolygon: Polygon Region

Description

Points inside polygon region.

Usage

inpolygon(x, y, xp, yp, boundary = FALSE)

Arguments

x, y

x-, y-coordinates of points to be tested for being inside the polygon region.

xp, yp

coordinates of the vertices specifying the polygon.

boundary

Logical; does the boundary belong to the interior.

Value

• Logical vector, the same length as x.

Details

For a polygon defined by points (xp, yp), determine if the points (x, y) are inside or outside the polygon. The boundary can be included or excluded (default) for the interior.

References

Hormann, K., and A. Agathos (2001). The Point in Polygon Problem for Arbitrary Polygons. Computational Geometry, Vol. 20, No. 3, pp. 131--144.

See Also

polygon

Examples

xp <- c(0.5, 0.75, 0.75, 0.5, 0.5)
yp <- c(0.5, 0.5, 0.75, 0.75, 0.5)
x <- c(0.6, 0.75, 0.6, 0.5)
y <- c(0.5, 0.6, 0.75, 0.6)
inpolygon(x, y, xp, yp, boundary = FALSE)  # FALSE
inpolygon(x, y, xp, yp, boundary = TRUE)   # TRUE

pg <- matrix(c(0.15, 0.75, 0.25, 0.45, 0.70,
               0.80, 0.35, 0.55, 0.20, 0.90), 5, 2)
plot(c(0, 1), c(0, 1), type="n")
polygon(pg[,1], pg[,2])
P <- matrix(runif(20000), 10000, 2)
R <- inpolygon(P[, 1], P[, 2], pg[, 1], pg[,2])
clrs <- ifelse(R, "red", "blue")
points(P[, 1], P[, 2], pch = ".", col = clrs)