The goal of nngeo is to provide k-nearest neighbor join capabilities for spatial analysis in R.
CRAN version -
install.packages("nngeo")GitHub version -
install.packages("devtools")
devtools::install_github("michaeldorman/nngeo")Once installed, the library can be loaded as follows.
library(nngeo)
#> Loading required package: sf
#> Linking to GEOS 3.5.1, GDAL 2.2.2, proj.4 4.9.2The following code section finds the 10-nearest towns for each city using function st_nn.
data(towns)
data(cities)
nn = st_nn(cities, towns, k = 20, progress = FALSE)
nn
#> [[1]]
#> [1] 29 40 87 2 49 43 9 11 63 36 37 52 10 44 46 70 48 65 39 35
#>
#> [[2]]
#> [1] 18 19 39 32 28 44 25 10 64 46 33 92 81 26 45 50 36 70 71 35
#>
#> [[3]]
#> [1] 69 80 61 68 60 58 30 57 89 56 22 7 24 78 13 84 6 3 59 20By default, the result is a sparse list with the neighbor IDs.
The st_nn function can also be used as a geometry predicate function when performing spatial join with sf::st_join.
nearest_towns = st_join(cities, towns, join = st_nn, k = 3, progress = FALSE)
head(nearest_towns)
#> Simple feature collection with 6 features and 2 fields
#> geometry type: POINT
#> dimension: XY
#> bbox: xmin: 34.78177 ymin: 31.76832 xmax: 35.21371 ymax: 32.0853
#> epsg (SRID): 4326
#> proj4string: +proj=longlat +datum=WGS84 +no_defs
#> name.x name.y geometry
#> 1 Jerusalem AMMINADAV POINT (35.21371 31.76832)
#> 1.1 Jerusalem ALMON POINT (35.21371 31.76832)
#> 1.2 Jerusalem ABU GHOSH POINT (35.21371 31.76832)
#> 2 Tel-Aviv AZOR POINT (34.78177 32.0853)
#> 2.1 Tel-Aviv ADANIM POINT (34.78177 32.0853)
#> 2.2 Tel-Aviv AHI'EZER POINT (34.78177 32.0853)A helper function st_connect can be used to draw lines according to joined feature IDs. This may be useful for visualization or for network analysis.
l = st_connect(cities, towns, ids = nn, progress = FALSE)
plot(st_geometry(towns), col = "darkgrey")
plot(st_geometry(cities), col = "red", add = TRUE)
plot(st_geometry(l), add = TRUE)