Performing nearest neighbor analysis

Nearest neighbor analysis relates one point to the nearest point in one or more datasets. In this recipe, we'll relate one set of points to the closest point from another dataset. In this case, we'll find the closest major city for each entry in a catalog of unidentified flying object (UFO) sightings from the National UFO reporting center. This analysis will tell you which major cities have the most UFO activity. The UFO catalog data just contains latitude and longitude points, so we'll use nearest neighbor analysis to assign names to places.

Getting ready

Download the following ZIP file and extract it to a directory named ufo in your qgis_data directory:

https://geospatialpython.googlecode.com/svn/ufo.zip

You will also need the MMQGIS plugin:

1. From the QGIS Plugins menu, select Manage and Install Plugins….
2. In the Plugins dialog search box, search for mmqgis.
3. Select the MMQGIS plugin and click on the Install plugin button.

How to do it...