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#
#
# density.psp.R
#
# $Revision: 1.19 $ $Date: 2021/03/01 01:04:39 $
#
#
density.psp <- function(x, sigma, ..., weights=NULL, edge=TRUE,
method=c("FFT", "C", "interpreted"),
at=NULL) {
verifyclass(x, "psp")
method <- match.arg(method)
w <- x$window
n <- x$n
if(length(weights)) {
check.nvector(weights, n, things="segments", oneok=TRUE, vname="weights")
if(length(weights) == 1) weights <- rep(weights, n)
} else weights <- NULL
len <- lengths_psp(x)
ang <- angles.psp(x, directed=TRUE)
ux <- unitname(x)
if(missing(sigma))
sigma <- 0.1 * diameter(w)
#' determine locations for evaluation of density
if(is.null(at)) {
atype <- "window"
w <- do.call.matched(as.mask, resolve.defaults(list(w=quote(w), ...)))
} else if(is.owin(at)) {
atype <- "window"
w <- do.call.matched(as.mask, resolve.defaults(list(w=quote(at), ...)))
} else {
atype <- "points"
atY <- try(as.ppp(at, W=w))
if(inherits(atY, "try-error"))
stop("Argument 'at' should be a window or a point pattern", call.=FALSE)
}
#' detect empty pattern
if(n == 0 || all(len == 0))
switch(atype,
window = return(as.im(0, w)),
points = return(rep(0, npoints(atY))))
#' determine prediction coordinates
switch(atype,
window = {
xy <- rasterxy.mask(w)
xx <- xy$x
yy <- xy$y
},
points = {
xx <- atY$x
yy <- atY$y
})
#' c o m p u t e
switch(method,
interpreted = {
#' compute matrix contribution from each segment
coz <- cos(ang)
zin <- sin(ang)
if(is.null(weights)) {
#' unweighted
for(i in seq_len(n)) {
en <- x$ends[i,]
dx <- xx - en$x0
dy <- yy - en$y0
u1 <- dx * coz[i] + dy * zin[i]
u2 <- - dx * zin[i] + dy * coz[i]
value <- dnorm(u2, sd=sigma) *
(pnorm(u1, sd=sigma) - pnorm(u1-len[i], sd=sigma))
totvalue <- if(i == 1L) value else (value + totvalue)
}
} else {
#' weighted
for(i in seq_len(n)) {
en <- x$ends[i,]
dx <- xx - en$x0
dy <- yy - en$y0
u1 <- dx * coz[i] + dy * zin[i]
u2 <- - dx * zin[i] + dy * coz[i]
value <- weights[i] * dnorm(u2, sd=sigma) *
(pnorm(u1, sd=sigma) - pnorm(u1-len[i], sd=sigma))
totvalue <- if(i == 1L) value else (value + totvalue)
}
}
dens <- switch(atype,
window = im(totvalue, w$xcol, w$yrow, unitname=ux),
points = totvalue)
},
C = {
#' C implementation of the above
xs <- x$ends$x0
ys <- x$ends$y0
xp <- as.numeric(as.vector(xx))
yp <- as.numeric(as.vector(yy))
np <- length(xp)
if(is.null(weights)) {
#' unweighted
z <- .C(SC_segdens,
sigma = as.double(sigma),
ns = as.integer(n),
xs = as.double(xs),
ys = as.double(ys),
alps = as.double(ang),
lens = as.double(len),
np = as.integer(np),
xp = as.double(xp),
yp = as.double(yp),
z = as.double(numeric(np)),
PACKAGE="spatstat.core")
} else {
#' weighted
z <- .C(SC_segwdens,
sigma = as.double(sigma),
ns = as.integer(n),
xs = as.double(xs),
ys = as.double(ys),
alps = as.double(ang),
lens = as.double(len),
ws = as.double(weights),
np = as.integer(np),
xp = as.double(xp),
yp = as.double(yp),
z = as.double(numeric(np)),
PACKAGE="spatstat.core")
}
dens <- switch(atype,
window = im(z$z, w$xcol, w$yrow, unitname=ux),
points = z$z)
},
FFT = {
Y <- pixellate(x, ..., weights=weights, DivideByPixelArea=TRUE)
dens <- blur(Y, sigma, normalise=edge, bleed=FALSE, ...)
if(atype == "points") dens <- dens[atY, drop=FALSE]
})
if(edge && method != "FFT") {
edg <- second.moment.calc(midpoints.psp(x), sigma, what="edge", ...)
switch(atype,
window = {
dens <- eval.im(dens/edg)
},
points = {
edgY <- edg[atY, drop=FALSE]
dens <- dens/edgY
})
}
if(atype == "window")
dens <- dens[x$window, drop=FALSE]
attr(dens, "sigma") <- sigma
return(dens)
}
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