Box plots are sometimes used to represent a range in a single value, but I am curious if a similar presentation would be useful in representing an overlaid column chart. By using the same color as the background for the minimum height column, the other columns can be made to float.
For a two-value overlaid column, the impact seems strong, making it very clear which item is larger and by how much.
With three values, clarity seems to noticeably decrease. Even adding a marker to indicate the missing column may not make the interpretation clear, though this presentation does seem to dramatize difference.
A comparison to a consistently intermediate value might be practical, but it then seems necessary to clarify that the lower bar descends to the value. This also seems to assume that the deficit/surplus quantity is significant.
With five values, the distortion effects seem significant since the comparisons are much less simple.
Even so there might be some datasets and purposes where a floating column chart with more than three values provides appropriately greater emphasis than a dot plot without confusion or deception.
Under what circumstances — if any — would such floating column charts be useful versus dot plots or more traditional (overlaid or adjacent) column charts?
How can the legend, fill choices, and other design elements make clear the overlaid nature, especially when comparing a larger number of values?
Table of Values
1Q14 2Q14 3Q14 4Q14 Ann 20 18 17 25 Bob 17 20 19 21 Celia 25 35 32 38 Dean 15 22 23 17 Ed 12 15 15 19