While working on a project in datacamp this week, I was using a log scale on a bar chart because it was the most effective way to communicate.  (NOTE: See this article from Naomi Robbins for more info about appropriate use of log scales.)  I ran into an interesting phenomenon in Tableau, which I believe is a bug, but I kind of like.

Let’s start with a simple bar chart with three different label alignment options.

Some quick notes:

1. The length of the bars in all of these examples is represented by the field “Value”
2. The label is represented by the field “% of Value”. 
3. These charts all use the default scale.

These charts look as I expect.  Auto, left and right align are placing the labels in the expected location.

However, look what happens when I change the scale to logarithmic.

What happened?

1. Auto alignment has suddenly become left align.
2. Left alignment is now right aligned, but inside the end of the bar.
3. Right alignment is now left aligned.

When I filter down to just the top 10, the behavior changes again.

Final thoughts:

1. I definitely think this is a bug, and I’ve reported this because Tableau is providing an inconsistent and unexpected user experience.
2. I really like the look of the bar label inside the end of the bar.  I would like more flexibility with label alignment to be able to get this look intentionally.
3. If you want to hear about lots of the cool stuff we’re doing with Tableau at Facebook, come here our talk at TCC13 at 11am on Wednesday – “Interworks: Data Discovery at Facebook: Why Culture & Flexibility Matter for Modern Analytics”.

If you want to play with it yourself, you can download the workbook here.