RapidPolygonLookup: An R package for polygon lookup using kd trees

Coordinate level spatial data need to be frequently aggregated to higher geographical identities like census blocks, ZIP codes or police district boundaries for analysis. This process requires mapping each point in the given data set to an individual element of the desired geographical hierarchy. Unless efficient data structures are used, this can be a daunting task. The operation point.in.polygon() from the package sp Pebesma and Bivand (2005) is computationally expensive. Here, we exploit kd-trees as an efficient nearest neighbor search algorithm to dramatically reduce the effective number of polygons being searched and expedite the lookup process.