What on earth is a Voronoi diagram? Put simply, it’s a graphical representation of proximity analysis that can be easily recognized by its characteristic cell-like structures. Each point in a Voronoi diagram is surrounded by a polygon (cell) that contains locations closer to it than to any other points. Google Search Mathematicians were informally using this type of diagram as early as the 17th century. However, it wasn’t until about a hundred years ago when Ukrainian mathematician Georgy Voronoi defined a solid mathematical theory supporting proximity analysis. READ THE WHOLE ARTICLE O ..read more

Maps are tricky, especially quantitative choropleth maps. Not because they are hard to make in Tableau. Just the opposite, it takes just a few mouse clicks to make one but is it right? It depends on the data. When you drop a continuous measure on the Filled Map, Tableau creates a choropleth map and assigns a unique shade of color to each mark – a sequential color palette. When your data is normally distributed, this default setup might be just what you need… … but it often isn’t and the color assignment requires further exploration. Overview of map classing Cartographers use several differen ..read more

If you’ve played with Tableau’s new spatial data connector, you might have come across an error like this: or even this: The first error message will pop up if you try to connect to a spatial file containing lines and the second when your spatial file contains more than one feature type. Geographic features can be polygons, lines or points. At the time of this writing, Tableau can connect to spatial files containing either polygons or points but not both in the same file. I don’t know if/when Tableau is planning to support mixed geometry spatial files but support for lines is a high priority ..read more

I recently had an opportunity to test the new spatial data connector in Tableau. It is a highly anticipated addition to the long list of connectors that allows you to work with ESRI Shapefiles, KML, MapInfo, and GeoJSON files directly in Tableau. The connector can interpret polygon and point entities (no lines as of yet) and is a big step towards making creation of maps in Tableau a much better experience. This long post is split into 2 parts, the first one describing preparation of data (which I did in FME) and the second part is about handling multiple shapefiles in Tableau to make the map w ..read more