Locate a point along a line

Returns how far along each line the closest position to the corresponding point lies, as a fraction between 0 and 1.

Usage

ga_line_locate_point(geometry, point)

Arguments

geometry

a GeoArrow linestring array

point

a GeoArrow point array; length 1 or the same length as geometry

Value

a double array of the same length as geometry

Details

0 is the start of the line and 1 its end, so the value multiplied by the line's length gives a distance. Only lines and linestrings can be located along; any other geometry type, a null geometry, a null point, or a zero length line becomes NA.

References

LineLocatePoint

See also

Other query: ga_closest_point(), ga_interior_point(), ga_is_convex()

Examples

line <- geoarrow::as_geoarrow_array(sf::st_sfc(
  sf::st_linestring(cbind(c(0, 10), c(0, 0)))
))
pt <- geoarrow::as_geoarrow_array(sf::st_sfc(sf::st_point(c(2.5, 0))))

as.vector(ga_line_locate_point(line, pt))
#> [1] 0.25