Non-Zero Axes: the big debate

I often argue that a chart’s y axis should always start with zero. Cole Nussbaumer (storytellingwithdata.com) and Jon Schwabish (policyviz.com) recently had a conversation about this very topic and posted it at storytellingwithdata.com, along with some example charts. In summary, Cole and Jon agreed that column/bar charts should always start their y-axis with zero. Because our eyes focus on the height of that bar, a non-zero axis distorts the relationship between columns. Savvy viewers of the chart may also be more skeptical about the truth of our visualization when they notice that the axis doesn’t start at zero.

But what if you really need to focus on small but meaningful differences between data points? Line graphs might be ok here depending on the context, because the focus in a line graph is on the relative position of the points in space rather than the height of the bars. But the relative positions can still be overstated by a non-zero axis.

One solution Cole and Jon (and I!) like is to present 2 charts side-by-side: one that has a zero-starting y axis to show the context of the data, and another that does not start at zero, but instead zooms into the chart to show the variation within a smaller range.

Non Zero Baseline Side by Side

Listen to the whole conversation at storytellingwithdata.com. Are there any examples in global health/development where a non-zero axis works?

Animation that Works: Visualizing the Population pyramid

Animation is a tricky thing.  It often seems to be added in to visualizations as a “bell” or “whistle” without any real meaning.  In that animated_pop_pyramidcase, it becomes a distraction, limiting focus on the data being displayed.

The Pew Research Center’s animated Population Pyramid, however, is a fabulous exception.   Years ago I tried to teach the population pyramid to a group of high schoolers.  How I wish this visualization existed then!   This animated visualization allows the reader to literally watch the population age, and simultaneously, the shifting shape from the pyramid to the rectangle.  This is far more effective and engaging than showing 20 static population pyramids in rapid succession.   The animation is also accompanied by a user-friendly explanation of demographic transformations.

Trust me, the static image above does not do justice to a population pyramid.  This animated visualization is worth a click!

Art made of data from TED

In today’s round up of great TED content, they shared a new feature on art made with data. While not always the most practical of examples, the work featured shows the beauty that can emerge through different visualization techniques and serve as great inspiration.

From TED:

Seeing patterns and creating beauty — data visualization has become an art form. Meet five artists who use spreadsheets, archives and digital data as their paints and canvas.

Check out their great interactive library here.