quadtree.extent([extent]) If extent is specified, expands the quadtree to cover the specified points [[x0, y0], [x1, y1]] and returns the quadtree. If extent is not specified, returns the quadtree’s current extent [[x0, y0], [x1, y1]], where x0 and y0 are the inclusive lower bounds and x1 and y1 are the inclusive upper bounds, or undefined if the quadtree has no extent. The extent may also be expanded by calling quadtree.cover or quadtree.add.

quadtree.addAll(data) Adds the specified array of data to the quadtree, deriving each element’s coordinates ⟨x,y⟩ using the current x- and y-accessors, and return this quadtree. This is approximately equivalent to calling quadtree.add repeatedly: for (var i = 0, n = data.length; i < n; ++i) { quadtree.add(data[i]); } However, this method results in a more compact quadtree because the extent of the data is computed first before adding the data.

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

quadtree.copy() Returns a copy of the quadtree. All nodes in the returned quadtree are identical copies of the corresponding node in the quadtree; however, any data in the quadtree is shared by reference and not copied.

quadtree.cover(x, y) Expands the quadtree to cover the specified point ⟨x,y⟩, and returns the quadtree. If the quadtree’s extent already covers the specified point, this method does nothing. If the quadtree has an extent, the extent is repeatedly doubled to cover the specified point, wrapping the root node as necessary; if the quadtree is empty, the extent is initialized to the extent [[⌊x⌋, ⌊y⌋], [⌈x⌉, ⌈y⌉]]. (Rounding is necessary such that if the extent is later doubled, the boundaries of

projection.translate([translate]) If translate is specified, sets the projection’s translation offset to the specified two-element array [tx, ty] and returns the projection. If translate is not specified, returns the current translation offset which defaults to [480, 250]. The translation offset determines the pixel coordinates of the projection’s center. The default translation offset places ⟨0°,0°⟩ at the center of a 960×500 area.

projection.stream(stream) Returns a projection stream for the specified output stream. Any input geometry is projected before being streamed to the output stream. A typical projection involves several geometry transformations: the input geometry is first converted to radians, rotated on three axes, clipped to the small circle or cut along the antimeridian, and lastly projected to the plane with adaptive resampling, scale and translation.

quadtree.add(datum) Adds the specified datum to the quadtree, deriving its coordinates ⟨x,y⟩ using the current x- and y-accessors, and returns the quadtree. If the new point is outside the current extent of the quadtree, the quadtree is automatically expanded to cover the new point.

projection.invert(point) Returns a new array [longitude, latitude] in degrees representing the unprojected point of the given projected point. The point must be specified as a two-element array [x, y] (typically in pixels). May return null if the specified point has no defined projected position, such as when the point is outside the clipping bounds of the projection. This method is only defined on invertible projections.

projection.scale([scale]) If scale is specified, sets the projection’s scale factor to the specified value and returns the projection. If scale is not specified, returns the current scale factor; the default scale is projection-specific. The scale factor corresponds linearly to the distance between projected points; however, absolute scale factors are not equivalent across projections.