Seth’s blog is always interesting, and usually I agree with him and learn something. However, when he discusses charts and graphs he’s often a very light  purple cow. This week he confirms that.

Godin’s The three laws of great graphs tells us that, when using graphs in presentations, we should follow these simple principles: “one story”, “no bar chars” and “motion”. Strange laws: a story with no substance, a caricature and motion without motion.

One Story per chart? No, one story per slide

“No, the reason you put a chart in a presentation is to tell a story. A single story, one story per chart. (…) There is no room for nuance here.”

Hmmm… story, no nuance. OK. But if a chart can only say “boy meets girl” isn’t there something missing?

A slide can be seen as an information unit (an “information chunk“) – that’s why Tufte writes about arranging things “adjacent in space rather than stacked in time”. It is the slide that tells the story, not the chart or any other single object. Actually, the presentation is your story – a slide is just a paragraph, a chart is just a sentence.

I can accept the idea of a nuance-free slide, but that doesn’t equal to an information-poor slide.

No bar charts – A caricature

Godin tells us that bar charts are overrated, and they should be replaced by a line/area chart (change over time) or a pie chart (comparing items at the same scale). You should use bar chart for before/after comparisons only.

I absolutely agree with Godin, you should never use bar charts – if your idea of a bar chart is similar to the one displayed in his post.

A nuance-free slide content is one thing, but different tools convey different messages, and you should be aware of those nuances. Time series 101: use bar charts to compare data points, use line charts to display trends. Categories 101: use pie charts to show proportions, use bar charts to rank data points.

Motion without motion

What Godin calls “motion” is just a silly dramatic effect for presentation purposes. “Look how fat I was”, and boom! “look how many pounds I’ve lost!” (fireworks and John Williams soundtrack). Motion can play a relevant role in presentations, but this is no motion, like a fake 3D chart is just a fake.

Bar graphs vs. pie charts

For whatever reasons, Godin decided to take a stance against bar charts. That’s ok, but his arguments are unfair (just look at the examples he uses in both blog posts). Let’s change the data in his second post and add meaningful trends to the time series:

Compare pie charts and bar charts

“Trolls are where we should focus our energy.” Are you sure? In his bar chart example there is no trend, no visible pattern. “There’s data here, but no information.” Well, just remove the unnecessary data. By the way, if the slices in a pie chart are labeled you don’t need a legend…

Do you really want three laws of great graphs? Here they are:

  • Tell a story;
  • Remove irrelevant data;
  • Choose the right messenger;
  • Bonus law: let the user write the story.
[Update: several “data presentation purists” are discussing this: