You can read the paper here.
Summary
I have come across the spie chart on the pie charts Wikipedia page. Following the link of the reference, I have found the paper by Dror Feitelson. The spie chart is described in the paper as the following:
Spie charts allow for an easy comparison of two partitions by combining two pie charts into one. The first pie chart serves as a base, and its partition sets the angle of each slice. The second pie chart is superimposed on the first, using the same angles. Its partition is then expressed by changing the radius of each slice so as to reflect its relative size. Slices that now extend beyond the circle of the original pie chart indicate that their relative size has grown, while slices that are smaller than the original circle indicate that their relative size has shrunk. This provides an immediate and visually striking display of the change from the first partition to the second one, at the price of losing the easy comparison of slice sizes for the second partition.
Whether the extension of the pie chart is by widening the angle or by pushing the wedge outwards, the values of each wedge are still difficult to get at one glance accurately. One can only get guesstimates and whether the changes are positive or negative from looking at a spie chart without labels. Instead of seeing labels as separate items from the chart itself, I think labels help users to get what the chart is showing quicker. Nonetheless, these are strictly my opinions, further research and surveys are definitely warranted to judge the effectiveness of the spie chart in transmitting information efficiently and precisely.
Here are 3 articles that I have come across supporting the use of spie chart with free access:
- Data on the Distribution of Cancer Incidence and Death across Age and Sex Groups Visualized using Multilevel Spie Charts (by the same author)
- Spie charts for quantifying treatment effectiveness and safety in multiple outcome network meta-analysis: A proof-of-concept study
- Spie charts, target plots, and radar plots for displaying comparative outcomes of health care (abstract only)
Things I Like
1. An in-depth description of the spie chart. I do enjoy the reading as it spends the entire paper discussing the new chart. This is something I have tried doing with the chart experiments posts on this blog. However, written by an academic, the paper is much better than what I do on this blog.
2. Admission of the problems of spie chart. As a paper written on spie charts, this paper does not exclude the problems of spie charts. I think the paper does capture the issues of the chart in an honest way, with the author addressing them in a systematic and thoughtful manner.
Verdict: A short paper worthy of anyone interested in innovating innovative charts.