Comments on: May you chop axes? No…you must!

By: Nicolas Bissantz

Nicolas Bissantz — Fri, 27 Feb 2009 18:23:55 +0000

Our dog-matic Bella would say: Always consider your design first, before daring to bend my Bella Reporting Standards. Paresh, I don't know your data, but it seems high delivery accuracy percentages is what you would expect. So, maybe you better show deviations from average or expected values and everything will be fine. Maybe this example is clarifying how this could be done.

By: paresh

paresh — Fri, 27 Feb 2009 15:24:12 +0000

Hi Nicolas,

I recently was doing a bar chart for delivery accuracy percentage for a number of stores where the percentages vary very marginally, between 95 % to 99.99 %. When the bar chart is part of the dashboard, the differences almost disappear. In this situation would it not be advisable to start from say 70. yes the rule of proportionality will be broken but the differences would clearly stand out.

By: Stephen Hampshire

Stephen Hampshire — Thu, 26 Feb 2009 12:57:52 +0000

I like Tufte’s advice to aim for an average angle of 45 degrees (bumpy, not spiky, not flat). That tends to give a picture that lets us read the true story most accurately.

That said, I think Chad’s point is very important – we must be consistent when the audience may be comparing between charts.

By: Adam

Adam — Tue, 24 Feb 2009 15:54:31 +0000

Very valid points.

Personally I first determine who my audience is…as you mention managing directors should be capable of reading the axis and not (pardon the pun) between the lines.

Another point, is that should you want to actually illustrate significant movements/difference etc. then I may chop the axes, and vice versa.

I would argue it wholly as it depends on the situation at the time. Unfortunately in this case, there’s no golden rule.

By: Nicolas Bissantz

Nicolas Bissantz — Tue, 24 Feb 2009 11:00:05 +0000

You are absolutely right, but the "always include zero" commandment often enough makes it even worse. Why not use logarithms?

By: Chad

Chad — Mon, 23 Feb 2009 21:23:57 +0000

Where this (chopping axes) really goes wrong is when multiple graphs are presented — for example, if there’s one graph per category, or separate graphs showing different metrics (say, sales and costs). Not including the zero point is quite dangerous in this case because readers can’t tell how the changes in categories or metrics compare to each other.