Create lines between features of two layers

Source: R/st_connect.R

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).

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)
#> lon-lat points
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)
#> lon-lat points
plot(st_geometry(towns), col = "darkgrey")
plot(st_geometry(l), add = TRUE)
plot(st_geometry(cities), col = "red", add = TRUE)


if (FALSE) {

# 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, search radius of 100 km
water = st_transform(water, 32636)
l = st_connect(water[-1, ], towns, k = 20, maxdist = 100000, 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, search radius of 100 km
l = st_connect(towns, water[-1, ], k = 2, maxdist = 100000)
plot(st_geometry(water[-1, ]), col = "lightblue", border = NA, extent = l)
plot(st_geometry(towns), col = "darkgrey", add = TRUE)
plot(st_geometry(l), col = "red", add = TRUE)

}