surveillance (version 1.5-4)

inside.gpc.poly: Test Whether Points are Inside a "gpc.poly" Polygon

Description

Same as, e.g., inside.owin from package spatstat and point.in.polygon from package sp, i.e., test whether points lie inside or outside a given polygon. Actually, the method for "gpc.poly" documented here internally uses the point.in.polygon function.

Usage

inside.gpc.poly(x, y = NULL, polyregion, mode.checked = FALSE)

Arguments

x,y

numeric vectors of coordinates of the points to be tested. The coordinates can be supplied in any form accepted by xy.coords.

polyregion

an object of class "gpc.poly". It is checked if the points specified through x and y fall into this polygonal region.

mode.checked

passed to point.in.polygon.

Value

• Logical vector whose ith entry is TRUE if the corresponding point (x[i],y[i]) is inside polyregion.

Details

The nodes and edges of (non-hole) polygons are treated as being inside. Points that fall strictly inside holes are treated as being outside of the polygon.

Examples

if (require("gpclib")) {
    oopt <- surveillance.options(gpclib=TRUE)
    poly <- discpoly(c(0.5,0.5), 0.5, npoly=4, class="gpc.poly")
    surveillance.options(oopt)
    pts <- cbind(x=runif(50), y=runif(50))
    plot(poly)
    points(pts, col=1+inside.gpc.poly(pts, polyregion=poly))
}