quadtree.find(x, y[, radius]) Returns the datum closest to the position ⟨x,y⟩ with the

quadtree.data() Returns an array of all data in the quadtree.

quadtree.cover(x, y) Expands the quadtree to cover the specified point ⟨x,y⟩, and returns the

quadtree.root() Returns the root node of the quadtree.

quadtree.size() Returns the total number of data in the quadtree.

quadtree.add(datum) Adds the specified datum to the quadtree, deriving its coordinates ⟨x,y⟩