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

[Roger Bivand]

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