Bump charts can be useful when visualizing how the rank of something changes over time. It can be particularly useful when comparing position or performance of something.
This blog will go through how to create a bump chart using Tableau.
1) Place your time variable in the columns tab and the value we are measuring in the rows tab. This should create a line graph.
2) Drag the variable that you want to rank into the color mark tab so that the line graph is split into multiple line graphs representing each variable.
3) For the graph in the example, the sub-categories need to be ranked by sum of sales over a quarterly period. To rank each category per quarter a table calculation needs to be made on the dimension we are measuring (SUM(Sales)).
4) In the table calculation window, the calculation type needs to be changed to 'Rank', and 'Descending'. In this example we would like the rank for each sub category, and would like the calculation to be reset every quarter. This is set by unchecking the time dimension in the 'compute using' section of this window. In this case, 'Quarter of Order Date' will be unchecked and the overall window will look as follows:
5) We can now edit the rank axis and reverse the axis so that the 1st rank will appear at the top.
6) The skeleton of the Bump chart is now complete and it is more about formatting now. Duplicate your time dimension next to your original one by dragging it from your side bar again.
There should be now two identical graphs in your view.
7) Change one of the graphs to circle and adjust the size of the resulting circles where needed.
8) To join the two graphs together they need to be placed on a dual synchronized axis. Right-click the second graphs axis and select 'Dual axis'. This will join the two graphs on the same axis. Right-click the axis again and select 'synchronize axis'.
8) To place the rank number within the circles, select labels on the circle marks tab. Select 'Show mark labels' and format the labels how you please. Set the vertical alignment to middle to move the rank numbers into the center of the circle.
