sfnetworks (version 0.4.1)

st_network_blend: Blend geospatial points into a spatial network

Description

Blending a point into a network is the combined process of first snapping the given point to its nearest point on its nearest edge in the network, subsequently splitting that edge at the location of the snapped point, and finally adding the snapped point as node to the network. If the location of the snapped point is already a node in the network, the attributes of the point (if any) will be joined to that node.

Usage

st_network_blend(x, y, tolerance = Inf, sort = FALSE)

Arguments

x

An object of class sfnetwork.

y

The spatial features to be blended, either as object of class sf or sfc, with POINT geometries.

tolerance

The tolerance distance to be used. Only features that are at least as close to the network as the tolerance distance will be blended. Should be a non-negative number preferably given as an object of class units. Otherwise, it will be assumed that the unit is meters. If set to Inf all features will be blended. Defaults to Inf.

sort

Should the nodes in the resulting network be sorted in the same order as those in x, followed by the new nodes blended in from y? Defaults to FALSE, meaning that node order might be changed.

Value

An object of class sfnetwork.

Examples

# NOT RUN {
library(sf, quietly = TRUE)

# Create a network and a set of points to blend.
n11 = st_point(c(0,0))
n12 = st_point(c(1,1))
e1 = st_sfc(st_linestring(c(n11, n12)), crs = 3857)

n21 = n12
n22 = st_point(c(0,2))
e2 = st_sfc(st_linestring(c(n21, n22)), crs = 3857)

n31 = n22
n32 = st_point(c(-1,1))
e3 = st_sfc(st_linestring(c(n31, n32)), crs = 3857)

net = as_sfnetwork(c(e1,e2,e3))

pts = net %>%
  st_bbox() %>%
  st_as_sfc() %>%
  st_sample(10, type = "random") %>%
  st_set_crs(3857) %>%
  st_cast('POINT')

# Blend points into the network.
# --> By default tolerance is set to Inf
# --> Meaning that all points get blended
b1 = st_network_blend(net, pts)
b1

# Blend points with a tolerance.
tol = units::set_units(0.2, "m")
b2 = st_network_blend(net, pts, tolerance = tol)
b2

## Plot results.
# Initial network and points.
par(mar = c(1,1,1,1), mfrow = c(1,3))
plot(net, cex = 2, main = "Network + set of points")
plot(pts, cex = 2, col = "red", pch = 20, add = TRUE)

# Blend with no tolerance
plot(b1, cex = 2, main = "Blend with tolerance = Inf")
plot(pts, cex = 2, col = "red", pch = 20, add = TRUE)

# Blend with tolerance.
within = st_is_within_distance(pts, st_geometry(net, "edges"), tol)
pts_within = pts[lengths(within) > 0]
plot(b2, cex = 2, main = "Blend with tolerance = 0.2 m")
plot(pts, cex = 2, col = "grey", pch = 20, add = TRUE)
plot(pts_within, cex = 2, col = "red", pch = 20, add = TRUE)

# }