[R-sig-Geo] How to efficiently generate data of neighboring points

[Lom Navanyo]

I tried looking at rtree package and even run the example at
https://github.com/hunzikp/rtree but it gives me the same error message
Error in UseMethod("withinDistance", rTree) :
   no applicable method for 'withinDistance' applied to an object of class
"c('list', 'RTree')"
That is strange given the page shows it was successful.

Regarding the library(spdep) and using dnearneigh(), I read through the
examples here https://r-spatial.github.io/spdep/reference/dnearneigh.html
but I seem to have a challenge as to how to get the output from wd1,wd2,
wd3, wd4  to my output object as in dataout.
For example when I call wd1, I get :
> wd1
Neighbour list object:
Number of regions: 101
Number of nonzero links: 38
Percentage nonzero weights: 0.3725125
Average number of links: 0.3762376
67 regions with no links:


How do I get the original point IDs and their respective neighbors IDs?

Lom





On Tue, Jun 2, 2020 at 11:29 AM Roger Bivand <Roger.Bivand using nhh.no> wrote:

> On Tue, 2 Jun 2020, Kent Johnson wrote:
>
> > rtree uses Euclidean distance so the points should be in a coordinate
> > system where this makes sense at least as a reasonable approximation.
>
> I tried the original example:
>
> remotes::install_github("hunzikp/rtree")
> library(spData)
> library(sf)
> projdata<-st_transform(nz_height, 32759)
> library(rtree)
> pts <- st_coordinates(projdata)
> rt <- RTree(st_coordinates(projdata))
> bufferR <- c(402.336, 1609.34, 3218.69, 4828.03, 6437.38)
> wd1 <- withinDistance(rt, pts, bufferR[1])
>
> but unfortunately failed (maybe newer Boost headers than yours?):
>
> Error in UseMethod("withinDistance", rTree) :
>    no applicable method for 'withinDistance' applied to an object of class
> "c('list', 'RTree')"
>
> Going back to the last century:
>
> library(spdep)
> bds <- c(0, bufferR)
> wd1 <- dnearneigh(pts, bds[1], bds[2])
> wd2 <- dnearneigh(pts, bds[2], bds[3])
> wd3 <- dnearneigh(pts, bds[3], bds[4])
> wd4 <- dnearneigh(pts, bds[4], bds[5])
>
> gives four neighbour objects. A neighbour object is an n-list of integer
> vectors (0 encodes no neighbours), which you can use to find the rows to
> copy out to your output object.
>
> Does this get you started?
>
> Roger
>
> >
> > Kent
> >
> > On Tue, Jun 2, 2020 at 9:59 AM Roger Bivand <Roger.Bivand using nhh.no> wrote:
> >
> >> On Tue, 2 Jun 2020, Kent Johnson wrote:
> >>
> >>>> Date: Tue, 2 Jun 2020 02:44:17 -0500
> >>>> From: Lom Navanyo <lomnavasia using gmail.com>
> >>>> To: r-sig-geo using r-project.org
> >>>> Subject: [R-sig-Geo] How to efficiently generate data of neighboring
> >>>>         points within specified radii (distances) for each point in a
> >> given
> >>>>         points data set.
> >>>>
> >>>
> >>>
> >>>> Hello,
> >>>> I have data set of about 3400 location points with which I am trying
> to
> >>>> generate data of each point and their neighbors within defined radii
> >> (eg,
> >>>> 0.25, 1, and 3 miles).
> >>>>
> >>>
> >>> The rtree package is very fast and memory-efficient for within-distance
> >>> calculations.
> >>> https://github.com/hunzikp/rtree
> >>
> >> Thanks! Does this also apply when the input points are in geographical
> >> coordinates?
> >>
> >> Roger
> >>
> >>>
> >>> Kent Johnson
> >>> Cambridge, MA
> >>>
> >>>       [[alternative HTML version deleted]]
> >>>
> >>> _______________________________________________
> >>> R-sig-Geo mailing list
> >>> R-sig-Geo using r-project.org
> >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>>
> >>
> >> --
> >> Roger Bivand
> >> Department of Economics, Norwegian School of Economics,
> >> Helleveien 30, N-5045 Bergen, Norway.
> >> voice: +47 55 95 93 55; e-mail: Roger.Bivand using nhh.no
> >> https://orcid.org/0000-0003-2392-6140
> >> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
> >>
> >
>
> --
> Roger Bivand
> Department of Economics, Norwegian School of Economics,
> Helleveien 30, N-5045 Bergen, Norway.
> voice: +47 55 95 93 55; e-mail: Roger.Bivand using nhh.no
> https://orcid.org/0000-0003-2392-6140
> https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en
>

	[[alternative HTML version deleted]]