No sorting and lack of structure undermine a chart

May 15, 2012

(This article was originally published at Junk Charts, and syndicated at StatsBlogs.)


Reader Daniel L. isn't impressed with this page of charts about gay rights in the U.S., from the Guardian paper (London). (link)


The use of circles to organize data has a long history, stretching back at least to the Nightingale rose, which turns the time dimension into a circle. Andrew doesn't like this concept (e.g. here), neither do I.  Here is something similar by McCandless (link) that has appeared on this blog.


Take the following set of charts showing the legislative differences by region of the country.


Since states within region are categories with no order, there is no easy way to order the states. This is made worse by the categorical nature of the other variable: the legislative posture on marriage, civil union and domestic partnership is very messy data with no order either.

The regions can be sorted reasonably by the "average" permissiveness but this chart shows no concern over sorting at all.

About the only easy read from this set of charts is the observation that the Northeast states are most permissive while the Southeast statements are most restrictive. Anyone who has casual exposure to this social issue knows this without needing a chart.


The key to clarifying this chart is to clarify the underlying structure, particularly the structure of the permissiveness variable. Dissecting the data reveals that there are only five possible postures (Banned all three rights, Banned marriage but allows one of the other rights, Allow civil unions, Allow marriage, and No information).  The following data table conveys the data with minimal fuss:




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