Which triangle is each point in? — find

For every point, the row of triangles whose triangle contains it, or NA for a point in none of them.

Usage

find_triangle(xy, triangles, points)

Arguments

xy: vertex coordinates, a two column matrix
triangles: one triangle per row, as three indices into xy
points: points to locate, a two column matrix

Value

An integer vector with one element per row of points.

Details

This is what the old tri_pip() did by building one sp polygon per triangle and calling over(). GEOS does the same job with a spatial index it builds for you: geos::geos_intersects_matrix() puts the triangles in an STRtree, so each point is only tested against the few whose bounding boxes it falls in. The exact containment test is then bary_weights(), in R.

Examples

xy <- cbind(c(0, 1, 1, 0), c(0, 0, 1, 1))
triangles <- rbind(c(1, 2, 3), c(1, 3, 4))
find_triangle(xy, triangles, cbind(c(0.9, 0.1, 5), c(0.5, 0.9, 5)))
#> [1]  1  2 NA