Old school D3 from simpler times

*k*-d tree nearest neighbors search
(*k*-NN). The red dots are the 10 nearest neighbors.
Orange dots are scanned and not selected.

Compare with this block that implements
a *k* nearest neighbor search using a quadtree instead of a *k*-d tree.

The algorithm for this search came from
this course handout.
Note that the "k" in *k*-d tree need not be the same number as the "k" in
the *k*-NN search. This is just the letter used to denote a positive integer
for both algorithms.

https://d3js.org/d3.v3.min.js