On 25/07/12 04:13, ASANTOS wrote:
Dear sig-geoers,
It's possible to making a multiple circular holes with owin()
function in spatstat package if the circles are created in a loop
function, for example:
##
##Circle x coordinates
x<-c(524237,524237,524237,524237,524237,524237,524237,524237,524242
,524242,524242,524247,524247,524247,524247,524247,524247,524247
,524247,524257,524257,524257,524257,524257,524257,524257)
##Circle x coordinates
You mean "##Circle y coordinates" here.
y<-c(7978856,7978866,7978876,7978896,7978916,7978936,7978946,7978956,7978956,7978946
,7978936,7978956,7978946,7978936,7978916,7978896,7978876,7978866
,7978856,7978856,7978876,7978896,7978906,7978916,7978936,7978956)
##
CIR<-NULL
points(a1.past.syn[,1],a1.past.syn[,2])
What on earth is the forgoing line all about? It adds nothing to
the issue of concern and makes your code non-reproducible.
We don't have "a1.past.syn".
for (i in 1:length(x)){
circle<-disc(radius=5,centre = c(x[i],y[i]))
CIR<-rbind(CIR, c(circle))
Using rbind() here makes no sense at all; actually c(circle) makes no
sense at all either.
}
Because I don't know, if I can use CIR's objet in the owin(poly = ...
) function, that uses list() for create this kind of object.
If your discs did not overlap you could just use owin(poly = ...) in the
following manner:
CIR <- vector("list",length(x))
for(i in 1:length(x)) CIR[[i]] <-
disc(radius=5,centre=c(x[i],y[i]))[["bdry"]][[1]]
W <- owin(poly=CIR)
***HOWEVER*** your discs *do* overlap, so the foregoing results in an
error and produces
no window. So what you have to/can do is:
CIR <- vector("list",length(x))
for(i in 1:length(x)) CIR[[i]] <- disc(radius=5,centre=c(x[i],y[i]))
W <- do.call(union.owin,CIR)
This takes quite a while --- order of half a minute or so on my elderly
laptop --- and
creates a window of type "mask".
If you really want a window with polygonal boundaries you need to
* be operating under conditions compatible with the gpclib license
* have the gpclib package installed
* enable gpclib by executing
spatstat.options(gpclib=TRUE)
before executing "W <- do.call(union.owin,CIR)". It's much quicker than
the "mask" type
implementation, but the fly in the ointment is that cotton pickin' license!
HTH
cheers,
Rolf Turner
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