# st_azimuth: Calculate the azimuth between pairs of points In michaeldorman/nngeo: k-Nearest Neighbor Join for Spatial Data

 st_azimuth R Documentation

## Calculate the azimuth between pairs of points

### Description

Calculates the (planar!) azimuth between pairs in two sequences of points `x` and `y`. When point sequence length doesn't match, the shorter one is recycled.

### Usage

``````st_azimuth(x, y)
``````

### Arguments

 `x` Object of class `sf`, `sfc` or `sfg`, of type `"POINT"` `y` Object of class `sf`, `sfc` or `sfg`, of type `"POINT"`

### Value

A `numeric` vector, of the same length as (the longer of) `x` and `y`, with the azimuth values from `x` to `y` (in decimal degrees, ranging between 0 and 360 clockwise from north). For identical points, an azimuth of `NA` is returned.

### Note

The function currently calculates planar azimuth, ignoring CRS information. For bearing on a sphere, given points in lon-lat, see function `geosphere::bearing`.

### Examples

``````# Two points
x = st_point(c(0, 0))
y = st_point(c(1, 1))
st_azimuth(x, y)

# Center and all other points on a 5*5 grid
library(stars)
m = matrix(1, ncol = 5, nrow = 5)
m[(nrow(m)+1)/2, (ncol(m)+1)/2] = 0
s = st_as_stars(m)
s = st_set_dimensions(s, 2, offset = ncol(m), delta = -1)
names(s) = "value"
pnt = st_as_sf(s, as_points = TRUE)
ctr = pnt[pnt\$value == 0, ]
az = st_azimuth(ctr, pnt)
plot(st_geometry(pnt), col = NA)
plot(st_connect(ctr, pnt, k = nrow(pnt), progress = FALSE), col = "grey", add = TRUE)
plot(st_geometry(pnt), col = "grey", add = TRUE)
text(st_coordinates(pnt), as.character(round(az)), col = "red")
``````

michaeldorman/nngeo documentation built on Jan. 10, 2024, 9:19 p.m.