Interpolate a point along a linestring

Returns the point at a given ratio or distance along each linestring, measured from either the start or end. The metric determines how distance is calculated.

Usage

ga_interpolate_point(line, value, metric, measure, from)

Arguments

line

a GeoArrow linestring array

value

a numeric vector of ratio or distance values; length 1 or the same length as line

metric

one of "euclidean", "haversine", "geodesic", or "rhumb"

measure

one of "ratio" or "distance"

from

one of "start" or "end"

Value

a GeoArrow point array

References

InterpolateLine

See also

Other interpolate: ga_point_at_distance_between(), ga_points_along_line()

Examples

line <- geoarrow::as_geoarrow_array(sf::st_sfc(
  sf::st_linestring(rbind(c(0, 0), c(10, 0)))
))

# halfway from the start, then two units in from the end
geoarrow::as_geoarrow_vctr(
  ga_interpolate_point(line, 0.5, "euclidean", "ratio", "start")
)
#> <geoarrow_vctr geoarrow.point{struct}[1]>
#> [1] <POINT (5 0)>
geoarrow::as_geoarrow_vctr(
  ga_interpolate_point(line, 2, "euclidean", "distance", "end")
)
#> <geoarrow_vctr geoarrow.point{struct}[1]>
#> [1] <POINT (8 0)>