Mythbusters: Should you start your axes at zero?

I’ve written before about the problem of “rules” and “laws” in data visualization. A classic one is “Thou must start your axes at zero.” If you’re reading my Brinton blog, go see what he had to say about it)

In this post I want to dispel this myth. It’s a myth that’s close to my heart. In August 2009 I went on the record (by commenting on The Guardian’s Datablog) that I disliked one of their charts because their axes didn’t start at zero.

andy comment

Let’s take the data from that Guardian article in order to investigate this Rule. Here’s how it looks with zero included:

with zero

This is bad for at least 4 reasons:

  1. It doesn’t really expose the change of the record over time.
  2. It especially doesn’t highlight the impact Usain Bolt had on the record.
  3. It doesn’t make great use of the space – there’s lots of dead space.
  4. It’s boring.

What happens when you break the rule?

without zero

 

All the problems are removed. It’s engaging, Usain Bolt’s impact is clear and it makes great use of space.

There’s one final reason not to include zero in this case. I do not know what the ultimate fastest time a human being will run 100m, but I can guarantee it isn’t zero seconds. My point is that not all measures you are charting have real zeros. In this case, the “zero” might be 9 seconds or so.

Once you learn the guidelines, you’ll be able to fine tune your charts by bending or breaking them according to your use case and objective. Sticking to the rules means you will satisfy the 5 criteria Alberto Cairo defines for a successful chart (he discussed these at his 2014 Tapestry Keynote):

  1. Truthful
  2. Functional
  3. Beautiful
  4. Insightful
  5. Enlightening

 

 

 

 

Iraq’s Bloody Toll: control your message with title, colour and orientation

Conside these charts. They have completely different messages and yet the only difference is the title, the colour and the orientation of the bars.

Creating a totally different message with just a title, axis and colour change.
Creating a totally different message with just a title, axis and colour change.

Watch the video below for an explanation, or go check out my slides from an older presentation, “Drive the message home with the right dashboard“. I also make this point in my Brinton talks, as he also covered this point.

Manual data collection

2014-10-14 09.32.18
My log of books/films/gigs

In the 21st century, the age of big data and the Internet of Things, it’s easy to get carried away logging everything you do in databases. I find there’s a charm and happiness in doing some data logging the old-fashioned way: on pen and paper.

What’s the log book above? I write down every book/film/gig/concert/play I read or see. I add a date and a score out of 5. I started the log in 2010. I was complaining to a friend, “Oh, I wish I’d kept a record of every book and gig I’d been to in my life.” It was probably the third time I’d had this conversation with her.

She replied, “Andy, quit bitching and just start one now.”

Good point. I did.

I love the physical object, and the easy nature of browsing back a few years. Sure, I could log this on Goodreads.com and equivalents, but it’s not the same. And part of me thinks it might be something I can share more easily with my kids one day. It’s also an anti-Tableau thing. I love Tableau but, you know what, sometimes I want my data to stay away from the screen. Unlike my music habits of course.

wanted to share another one we received at work recently – this is data collected about Premier League players by someone when they were 8 years old:

IMG_0918

 

Do you collect data? Post a link in the comments below or on Twitter. Let’s share our manual data logs. Geeks of the world: Unite!