Spotfire® Tips & Tricks: Bump Charts with Spotfire

Introduction

 Bump Charts are popular for exploring the changes in the Rank of a value over a time dimension or place dimension or any other dimension relevant to the analysis. The name originated from a boat race where each boat tries to bump their boat and move up the race. They are very useful for compactly highlight trends and are also known as junk charts. A crisscross in a bump chart indicates one entity has surpassed another in absolute terms even when comparison is based on relative ranks

Easy Steps to create a Bump Chart in Spotfire

In order to create a Bump chart, we need a ranked data set. As an example Times Higher Education World Reputation Rankings data for the top 10 universities by reputation was used. The Times Higher Education World Reputation Rankings employ the world's largest invitation-only academic opinion survey to provide the definitive list of the top 100 most powerful global university brands. A list of top 10 University for the year 2017 was selected and then earlier ranks for the years 2016 until 2012 was added.

Data was updated to indicate relative rank instead of overall rank out of 100.

A line chart with X-axis as Column Names, Y-axis as multiple dimensions and color by Institute would create a bump chart as shown in the figure.

Spotfire easily lets you highlight a line in bump charts to see the Institute name and changes in rank effectively Highlighting with help of marking and a tooltip makes it apparent that Stanford has zigzagged a lot in terms of Rank and Berkeley has shown a dip in 2014.

It is also possible to use Parallel Coordinate Plot as Bump Chart but in that case, a calculation is required to give more importance to the highest Rank. A calculated column abs([actual rank]-lowest rank-1) was used to calculate the modified rank and this new rank was used in a parallel coordinate plot to display the bump chart as shown in the figure.

You can clearly figure Harvard has maintained its reputation at number 1 with Yale and Princeton having never got "Bumped".