R/polysph.area.Wr.int.R

In baddstats/spherstat: Spatial Point Pattern Analysis, Geometry and Trigonometry for the Sphere

polysph.area.Wr.int <- function(win, r=0) {
	stopifnot(inherits(win, c("sp2", "sp3", "sphwin")))
	if(inherits(win, "sphwin")) {
		win <- win
	}
	else {
		win <- win$win
	}
	stopifnot(win$type=="polygon" || win$type == "wedge")
	rad <- win$rad
	area.W <- area.sphwin(w=win)
	lr <- length(r)
	aW <- switch(win$type,
		wedge = {
			phi <- pi/2 - r/rad
			theta <- win$param[1]/2
			h <- pi - 2*sphsin(d1=r, d2=NULL, theta1=theta, theta2=pi/2, rad=rad)
			psi0 <- 2*sphcos(d1=phi, d2=phi, d3=h, theta=NULL, rad=1)*rad
			csp <- cumsum(rev(psi0))
			area.Wr <- rev(c(0, csp[1:(lr-1)]*(r[2]-r[1])))*(rad^2)
			area.Wr*(area.W/max(area.Wr))
		},
		stop("Unsupported window type")
	)
	aW
}