Combining geographical information and traditional plots: the checkerplot

Abstract

The checkerplot is a new type of graphical display that combines geographical information and statistical plots. Hereby, the traditional plots like barplots or polygon lines are visualized in geographical order on a grid. The checkerplots can be seen as a mixture between thematic maps and the grid representation in trellis plots.

In a checkerplot, any complex statistical graphics that are produced for geographical areas are placed in a grid. An interpretable checkerplot requires an arrangement of areas on the grid that reflects the underlying geography. A loss function is proposed that represents the distortion of the underlying geography needed in order to place the areas onto a grid. It is demonstrated that the minimization of the loss function does indeed produce interpretable checkerplots. Moreover, the optimization problem can be formulated as a linear programming problem that can be solved using standard linear programming solvers.

The proposed checkerplot is applied to US health insurance data to analyze the development of the coverage rate in the health system per state with respect to the different health care programs. Moreover, an example related to the EU-member states is also given. Additional information like the national flags of countries are placed in each grid to allow better visibility and recognition of the countries.

The checkerplot is implemented in the R-package sparkTable (Kowarik, Meindl, and Templ, 2012. sparkTable: sparklines and graphical tables for tex and html [online]. R package version 0.9.3 [Accessed 7 February 2012]) and can be freely downloaded from the CRAN repository. It is implemented in a flexible manner and not restricted to the examples given in this contribution.

Keywords:

• statistical graphics
• geographical information
• linear programming
• R

Acknowledgments

This work was partly funded by the European Union (represented by the European Commission) within the 7th framework programme for research (Theme 8, Socio-Economic Sciences and Humanities, Project AMELI (Advanced Methology for European Laeken Indicators), Grant Agreement No. 217322). Visit http://ameli.surveystatistics.net for more information on the project.

Notes

1. see, e.g., http://www.census.gov/geo/www/tiger/tgrshp2011/tgrshp2011.html

2. (http://www.opencongress.org/bill/111-h3590/show [Accessed 2 September 2011])