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#
# xysegment.S
#
# $Revision: 1.18 $ $Date: 2017/02/20 06:27:10 $
#
# Low level utilities for analytic geometry for line segments
#
# author: Adrian Baddeley 2001
# from an original by Rob Foxall 1997
#
# distpl(p, l)
# distance from a single point p = (xp, yp)
# to a single line segment l = (x1, y1, x2, y2)
#
# distppl(p, l)
# distances from each of a list of points p[i,]
# to a single line segment l = (x1, y1, x2, y2)
# [uses only vector parallel ops]
#
# distppll(p, l)
# distances from each of a list of points p[i,]
# to each of a list of line segments l[i,]
# [interpreted code uses large matrices and 'outer()']
# [Fortran implementation included!]
distpl <- function(p, l) {
xp <- p[1]
yp <- p[2]
dx <- l[3]-l[1]
dy <- l[4]-l[2]
leng <- sqrt(dx^2 + dy^2)
# vector from 1st endpoint to p
xpl <- xp - l[1]
ypl <- yp - l[2]
# distance from p to 1st & 2nd endpoints
d1 <- sqrt(xpl^2 + ypl^2)
d2 <- sqrt((xp-l[3])^2 + (yp-l[4])^2)
dmin <- min(d1,d2)
# test for zero length
if(leng < .Machine$double.eps)
return(dmin)
# rotation sine & cosine
co <- dx/leng
si <- dy/leng
# back-rotated coords of p
xpr <- co * xpl + si * ypl
ypr <- - si * xpl + co * ypl
# test
if(xpr >= 0 && xpr <= leng)
dmin <- min(dmin, abs(ypr))
return(dmin)
}
distppl <- function(p, l) {
xp <- p[,1]
yp <- p[,2]
dx <- l[3]-l[1]
dy <- l[4]-l[2]
leng <- sqrt(dx^2 + dy^2)
# vector from 1st endpoint to p
xpl <- xp - l[1]
ypl <- yp - l[2]
# distance from p to 1st & 2nd endpoints
d1 <- sqrt(xpl^2 + ypl^2)
d2 <- sqrt((xp-l[3])^2 + (yp-l[4])^2)
dmin <- pmin.int(d1,d2)
# test for zero length
if(leng < .Machine$double.eps)
return(dmin)
# rotation sine & cosine
co <- dx/leng
si <- dy/leng
# back-rotated coords of p
xpr <- co * xpl + si * ypl
ypr <- - si * xpl + co * ypl
# ypr is perpendicular distance to infinite line
# Applies only when xp, yp in the middle
middle <- (xpr >= 0 & xpr <= leng)
if(any(middle))
dmin[middle] <- pmin.int(dmin[middle], abs(ypr[middle]))
return(dmin)
}
distppll <- function(p, l, mintype=0,
method=c("C", "Fortran", "interpreted"), listit=FALSE) {
np <- nrow(p)
nl <- nrow(l)
xp <- p[,1]
yp <- p[,2]
if(is.na(match(mintype,0:2)))
stop(paste("Argument", sQuote("mintype"), "must be 0, 1 or 2.\n"))
method <- match.arg(method)
if(method == "Fortran") {
warning("method='Fortran' is no longer supported; method='C' was used")
method <- "C"
}
switch(method,
interpreted={
dx <- l[,3]-l[,1]
dy <- l[,4]-l[,2]
# segment lengths
leng <- sqrt(dx^2 + dy^2)
# rotation sines & cosines
co <- dx/leng
si <- dy/leng
co <- matrix(co, nrow=np, ncol=nl, byrow=TRUE)
si <- matrix(si, nrow=np, ncol=nl, byrow=TRUE)
# matrix of squared distances from p[i] to 1st endpoint of segment j
xp.x1 <- outer(xp, l[,1], "-")
yp.y1 <- outer(yp, l[,2], "-")
d1 <- xp.x1^2 + yp.y1^2
# ditto for 2nd endpoint
xp.x2 <- outer(xp, l[,3], "-")
yp.y2 <- outer(yp, l[,4], "-")
d2 <- xp.x2^2 + yp.y2^2
# for each (i,j) rotate p[i] around 1st endpoint of segment j
# so that line segment coincides with x axis
xpr <- xp.x1 * co + yp.y1 * si
ypr <- - xp.x1 * si + yp.y1 * co
d3 <- ypr^2
# test
lenf <- matrix(leng, nrow=np, ncol=nl, byrow=TRUE)
zero <- (lenf < .Machine$double.eps)
outside <- (zero | xpr < 0 | xpr > lenf)
if(any(outside))
d3[outside] <- Inf
dsq <- matrix(pmin.int(d1, d2, d3),nrow=np, ncol=nl)
d <- sqrt(dsq)
if(mintype >= 1)
min.d <- apply(d, 1, min)
if(mintype == 2)
min.which <- apply(d, 1, which.min)
},
# Fortran code removed!
# Fortran={
# eps <- .Machine$double.eps
# if(mintype > 0) {
# big <- sqrt(2)*diff(range(c(p,l)))
# xmin <- rep.int(big,np)
# } else {
# xmin <- 1
# }
# n2 <- if(mintype > 1) np else 1
# temp <- DOTFortran("dppll",
# x=as.double(xp),
# y=as.double(yp),
# l1=as.double(l[,1]),
# l2=as.double(l[,2]),
# l3=as.double(l[,3]),
# l4=as.double(l[,4]),
# np=as.integer(np),
# nl=as.integer(nl),
# eps=as.double(eps),
# mint=as.integer(mintype),
# rslt=double(np*nl),
# xmin=as.double(xmin),
# jmin=integer(n2))
# d <- matrix(temp$rslt, nrow=np, ncol=nl)
# if(mintype >= 1)
# min.d <- temp$xmin
# if(mintype == 2)
# min.which <- temp$jmin
# },
C = {
eps <- .Machine$double.eps
temp <- .C(C_prdist2segs,
x=as.double(xp),
y=as.double(yp),
npoints =as.integer(np),
x0=as.double(l[,1]),
y0=as.double(l[,2]),
x1=as.double(l[,3]),
y1=as.double(l[,4]),
nsegments=as.integer(nl),
epsilon=as.double(eps),
dist2=as.double(numeric(np * nl)),
PACKAGE = "spatstat.utils")
d <- matrix(sqrt(temp$dist2), nrow=np, ncol=nl)
if(mintype == 2) {
min.which <- apply(d, 1, which.min)
min.d <- d[cbind(1:np, min.which)]
} else if (mintype == 1) {
min.d <- apply(d, 1, min)
}
})
###### end switch #####
if(mintype==0)
return(if(listit) list(d=d) else d)
else if(mintype==1)
return(list(d=d, min.d=min.d))
else if(mintype==2)
return(list(d=d, min.d=min.d, min.which=min.which))
}
# (distance to) nearest segment
distppllmin <- function(p, l, big=NULL) {
np <- nrow(p)
nl <- nrow(l)
if(is.null(big)) {
xdif <- diff(range(c(p[,1],l[, c(1,3)])))
ydif <- diff(range(c(p[,2],l[, c(2,4)])))
big <- 2 * (xdif^2 + ydif^2)
}
z <- NNdist2segments(p[,1], p[,2],
l[,1], l[,2], l[,3], l[,4],
big)
return(list(min.d=sqrt(z$dist2), min.which=z$index))
}
NNdist2segments <- function(xp, yp, x0, y0, x1, y1, bigvalue) {
np <- length(xp)
ns <- length(x0)
dist2 <- rep(bigvalue, np)
z <- .C(C_nndist2segs,
xp=as.double(xp),
yp=as.double(yp),
npoints=as.integer(np),
x0=as.double(x0),
y0=as.double(y0),
x1=as.double(x1),
y1=as.double(y1),
nsegments=as.integer(ns),
epsilon=as.double(.Machine$double.eps),
dist2=as.double(dist2),
index=as.integer(integer(np)),
PACKAGE = "spatstat.utils")
return(list(dist2=z$dist2,
index=z$index + 1L))
}
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