The 5th Day of Analytics – Buffer

Carrying on with The 12 Analytics of Christmas, let’s take a look at one of the simplest yet most powerful analytics feature – Buffer. In a nutshell, Buffer allows you to set a perimeter around your points, lines or polygons by a specified distance. So if you want to show a ‘noise’ perimeter around a road or display transit stops within 100 m. radius of your store, the buffer comes in handy.

To better illustrate the functionality, let’s create a simple analysis of all Washington DC metro stations with 500m buffer. Here is how it works.

1. Grab metro stations data set from Geocommons.
2. Click on Analyze Data and select Buffer option.
3. In the Buffer menu, specify the distance parameter and you are done!

Here is the beautiful resulting map.

One thing to keep in mind is that buffer areas look skewed because of the map projection – this is why in the example above the buffer areas are displayed as ellipsoids rather than circles.