Wednesday, 22 February 2012

The Dorling Cartogram

My last project involved using a multitude of regions for drawing analysis, parallels and comparison. Not wanting to use yet another Choropleth graph, I decided to look up alternatives which were easier to create and preferably required no VBA.

Soon I stumbled upon "The Dorling Cartogram", defined in the UCSB site as, "This type of cartogram was named after its inventor, Danny Dorling of the University of Leeds. A Dorling cartogram maintains neither shape, topology nor object centroids, though it has proven to be a very effective cartogram method. To create a Dorling cartogram, instead of enlarging or shrinking the objects themselves, the cartographer will replace the objects with a uniform shape, usually a circle, of the appropriate size."

I had the data for Obesity in the United States handy, so I decided to give it a try before using it in my project. I opted to use Bubble charts because data points within a series may need to be of varied shapes based on its obese population while the colors indicated different tiers of obesity percentage. Thus larger the circle and redder it is, the severe the obesity. To determine the obese population per state, I have used 1990 Census data to calculate between 1995-2000 and the 2000 Census data to calculate between 2001-2010.

My version of Dorling Cartogram in Excel:

Parting words: As Dorling Cartograms are non-overlapping. In places they overlapped, it is common practice they rather be moved so that the full area of each shape can be seen. The positions of several states in relation to each other are hence slightly altered as per this principle.

Friday, 10 February 2012

The Pie-Doughnut Combination: A Radial Treemap

I stumbled into this graph some years ago, while looking up data for a project on US Auto Sales, through a post in Neoformix - Discovering and Illustrating Patterns in Data. So, when I started making the list of Pie-Doughnut combination charts, I decided to include this variety and use it to display survivors and victims of the Titanic tragedy on its centenary year. 

It is not a particularly difficult chart to create, specially if one sets up the table properly. My first attempt brought me this:

I thought a lot over whether to keep the statistics as labels for the outermost doughnut that displayed the survivor/victim proportions. They get a bit muddled up around the first class women and children' section and the inability to add leader lines to the doughnut labels meant they couldn't be dragged away and the lines used as pointers.

Here is the chart with the stats on display:

Thursday, 2 February 2012

The Pie-Doughnut Combination: A Fan Plot

Happy to be back after a pretty busy beginning to the new year. I had this completed almost immediately following the preceding post, but was otherwise hard pressed to find a suitable time to post it.

Soon after writing the Florence Nightingale Circumplex Chart post, I started searching for more varieties of charts that can be created using combinations of Pie-Doughnut charts. Soon enough, I found one through Naomi B. Robbins' comment in a Jorge Camoes' post.

The referenced PDF article attempts to use Fan Plot to display relative quantities and differences using the R statistical language as is shown in the image below.

Impassive to its benefits and/or disadvantages, I created it in Excel.