I'm trying to use R's terra::nearest() function, but I cannot understand the output format and how to actually figure out which point was nearest! Here's a simple example:
> dest <- terra::vect(data.frame(x = c(0, 0, 5, 5), y = c(0, 5, 0, 5), attr = 1:4), geom = c("x", "y"))
> src <- terra::vect(data.frame(x = c(3, 1, 2), y = c(2, 3, 1)), geom = c("x", "y"))
> near_ret <- terra::nearest(src, dest)
> print(near_ret)
class : SpatVector
geometry : points
dimensions : 3, 7 (geometries, attributes)
extent : 0, 5, 0, 5 (xmin, xmax, ymin, ymax)
coord. ref. :
names : from_id from_x from_y to_id to_x to_y distance
type : <num> <num> <num> <num> <num> <num> <num>
values : 1 3 2 1 5 0 2.828
2 1 3 2 0 5 2.236
3 2 1 3 0 0 2.236
OK, so to_x, to_y and distance columns make sense to me and look correct. But to_id doesn't make any sense to me. I would have assumed that column would have indexes into dest, but it clearly does not because dest[1, ] is (0, 0) not (5, 0).
My end goal here is to figure out the value of attr for the dest point closest each src point. How can I find the dest point which is closest so that I can look up it's attr value?
(This is using terra version 1.3-4)
This bug was fixed in terra version 1.4-4