distanceto (version 0.0.3)

distance_to: Distance to

Description

Measures the distance from points x to features in layer y.

Usage

distance_to(x, y, measure = NULL)

Value

A vector of distances from points in x to features in layer y.

Arguments

x

points to measure distances from, to layer y. Expecting an sf point compatible with sf::st_coordinates such as an sf, sfc or sfg object with geometry type 'POINT' or 'MULTIPOINT'. CRS of x should match CRS of y.

y

feature layer to measure distance to. Expecting an sf point, line or polygon compatible with sf::st_coordinates such as an sf, sfc or sfg object. CRS of y should match CRS of x.

measure

method used to measure geographic distances between longlat x and y objects. See geodist::geodist for more information. Ignored if CRS of x and y indicated projected coordinates.

Details

Uses the function nabor::knn to determine the distance from each point in x to the nearest feature in layer y. If the input CRS is longlat, eg. EPSG 4326, the distance is returned as measured by geodist::geodist. Otherwise, if the input CRS indicates projected coordinates, the distance returned is the euclidean distance. Both x and y are expected to be sf objects and the distances are returned as vector, easily added to input x with $<- or other methods. If y is a 'POLYGON' or 'MULTIPOLYGON' object, the distance returned for points in x within features in y are set to 0.

Examples

# Load sf
library(sf)

# Load nc data
nc <- st_read(system.file("shape/nc.shp", package="sf"))

# Set number of sampling points
npts <- 1e3

# Note: package 'lwgeom' required for st_sample
if (require(lwgeom, quietly = TRUE)) {
  # Sample points in nc
  ncpts <- st_sample(nc, npts)

	# Select first 5 of nc
	ncsub <- nc[1:5,]

	# Measure distance from ncpts to first 5 of nc, printing result
	distance_to(ncpts, ncsub, measure = 'geodesic')

	# or add to ncpts
	ncpts$dist <- distance_to(ncpts, ncsub, measure = 'geodesic')
}