nngeo: st_connect – R documentation

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st_connect

Create lines between features of two layers

Description

Returns a line layer with line segments which connect the nearest feature(s) from y for each feature in x. This is mostly useful for graphical purposes (see Note and Examples below).

Usage

st_connect(x, y, ids = NULL, progress = TRUE, ...)

Arguments

`x`	Object of class `sf` or `sfc`
`y`	Object of class `sf` or `sfc`
`ids`	A sparse list representation of features to connect such as returned by function `st_nn`. If `NULL` the function automatically calculates `ids` using `st_nn`
`progress`	Display progress bar? (default `TRUE`)
`...`	Other arguments passed to `st_nn` when calculating `ids`, such as `k` and `maxdist`

Value

Object of class sfc with geometry type LINESTRING

Note

The segments are straight lines, i.e., they correspond to shortest path assuming planar geometry regardless of CRS. Therefore, the lines should serve as a graphical indication of features that are nearest to each other; the exact shortest path between features should be calculated by other means, such as geosphere::greatCircle.

Examples

# Nearest 'city' per 'town'
l = st_connect(towns, cities, progress = FALSE)
plot(st_geometry(towns), col = "darkgrey")
plot(st_geometry(l), add = TRUE)
plot(st_geometry(cities), col = "red", add = TRUE)

# Ten nearest 'towns' per 'city'
l = st_connect(cities, towns, k = 10, progress = FALSE)
plot(st_geometry(towns), col = "darkgrey")
plot(st_geometry(l), add = TRUE)
plot(st_geometry(cities), col = "red", add = TRUE)

## Not run: 

# Nearest 'city' per 'town', search radius of 30 km
cities = st_transform(cities, 32636)
towns = st_transform(towns, 32636)
l = st_connect(cities, towns, k = nrow(towns), maxdist = 30000, progress = FALSE)
plot(st_geometry(towns), col = "darkgrey")
plot(st_geometry(l), add = TRUE)
plot(st_buffer(st_geometry(cities), units::set_units(30, km)), border = "red", add = TRUE)

# The 20-nearest towns for each water body
water = st_transform(water, 32636)
l = st_connect(water[-1, ], towns, k = 20, dist = 100, progress = FALSE)
plot(st_geometry(water[-1, ]), col = "lightblue", border = NA)
plot(st_geometry(towns), col = "darkgrey", add = TRUE)
plot(st_geometry(l), col = "red", add = TRUE)


# The 2-nearest water bodies for each town
l = st_connect(towns, water[-1, ], k = 2, dist = 100)
plot(st_geometry(water[-1, ]), col = "lightblue", border = NA)
plot(st_geometry(towns), col = "darkgrey", add = TRUE)
plot(st_geometry(l), col = "red", add = TRUE)


## End(Not run)

nngeo

k-Nearest Neighbor Join for Spatial Data

v0.4.2

MIT + file LICENSE

Authors

Michael Dorman [aut, cre], Johnathan Rush [ctb], Ian Hough [ctb], Dominic Russel [ctb], Luigi Ranghetti [ctb], Charles F.F Karney [ctb, cph] (Author of included C code from 'GeographicLib' for geodesic distance)

Initial release