Alteryx Mapping: US at Night

[ned_blog]

Click here for more variables

I love maps.  A picture is truly worth a thousand words.  Creating a great map is writing a story.  Sometimes that story tells the viewer what to think and sometimes it conveys information that lets them reach their own conclusion.

My goal for Alteryx is that it is the Swiss Army knife for Data Artisans.  I wanted to create a set of maps to inspire and show the what Alteryx can do.  The power really is in the hands of the Data Artisan.

The goal of this map was to present raw demographic data as if it was a nighttime photo from space.  I want to let the viewer write their own story in their mind and this is an image that is familiar, even if they haven’t seen anything quite like it before.  The cool thing about demographics is that the map can be re-drawn for any subset of people in the country.  If the Total Population map represents every individual with a light on, the Asian Population map, for instance, is as if everyone in the country who is not Asian turned off their lights.  The Asian Population represents the same amount of light in the Total Population map as is seen in the Asian Population map.  This means that the subset maps convey both the location of a population as well as the size.  Click on the above map (or here) for a larger version and a lot more variables to explore.

Technical Details – or How to make your own cool maps:

Even though this looks like some sort of photograph, it is a regular themed map generated by Alteryx.  The process starts by generating grid cells that exactly line up with the final pixels on the map.  This is a little different than the regular Make Grid tool which makes grids that are all the same size in square miles.  These grid cells are all the same size on the rendered map, but they vary between about 9 and 10 square miles depending on the position on the earth.

Once the grid polygons are generated, it is a simple matter to send them through the Allocate Append tool to apply 1 or more demographic variables.  This is very simple to use, but Alteryx has a lot of math (and magic) behind the scenes.

In order to generate the theme, the variable is normalized to the number of square miles and then we take a logarithm of it to make the final theme an exponential scale.  On the Report Map  tool, we specify manual cutoffs so that 100 people represents the same shade of gray regardless of the variable.  If we let the scale be automatic, it would brighten up the subsets in relation to the total pop map.

Between generating the polygons (over 900,000 of them!) , applying demographics and painting the PNG, there is a ton of computing power going in to one of these maps – so it is pretty amazing that each map is rendered in between 15 and 60 seconds on a desktop.

With a (free) Alteryx Gallery account, you can run maps for variables you pick, although the free accounts are limited to the US Census SF1 data set.  Click here to go straight to the app in the public gallery.  If you download the app and run it in your copy of Alteryx, you can run these maps for any dataset or country you have available.  What’s even cooler is that the US Census DVDs are in Alteryx/Allocate format; so if you order the data from them (for free!) you can use it directly in the free version of Alteryx.

Thanks for listening,

ned.

If you don’t yet have a copy of Alteryx yet, by all means go get one.  Its free (for limited use)…http://www.alteryx.com/download

This post originally appeared at:http://alteryxned.wordpress.com/2013/08/30/alteryx-mapping-us-at-night/