Using diffusion-based cartograms for visual representation and exploratory analysis of plausible study hypotheses: the small and big belly effect

摘要

Diffusion-based cartograms provide a new, more innovative way to visually explore and represent spatial data than do standard maps. In this study, we explore two basic issues regarding visual effectiveness and expressiveness of diffusion-based cartograms: first, we evaluate different applications to support our study hypotheses; and second, we evaluate the visual effectiveness of the resulting maps using five criteria: attribute values, colour, labels, readability of maps, and clusters. Besides, diffusion-based cartograms are compared to standard choropleth mapping to illustrate the additional visual exploratory power these cartograms have to offer. Recent studies have shown that diffusion-based cartograms can facilitate the uncovering of underlying and hidden structures, thus providing a more elaborate visual representation of attribute value than conventional mapping does. Interestingly, the ability to display and visualize small areas and geographic locations with high attribute values using diffusion-based cartograms also allows for comprehensive exploration and identification of specific geographies that are normally difficult to visually observe with conventional maps. This method was applied to the results of the US incidence of child lead poisoning, Tanzania’s infant mortality, Uganda’s 2006 presidential election and South Korea’s 2005 population. These applications have yielded a number of new insights into the datasets illustrating ‘the small and big belly effect’ while successfully confirming the benefits of using diffusion-based cartograms.