Datawrapper is a tool that lets you turn a dataset into a decent-looking chart within minutes. In an interview, co-founder Mirko Lorenz said Datawrapper is designed to prevent people making misleading graphs:
With Datawrapper, we try to make it as hard as possible to take data and create misleading charts with it. For example, it’s not possible to create bar charts with cropped axes. From time to time, users ask us to add this feature, but we never have and we never will. (via)
This may sound a bit paternalistic but it makes sense: Datawrapper’s philosophy is to offer a simple, robust way to quickly create a chart. If you don’t like the limitations, learn to code D3.js.
But Lorenz’ remark made me curious: would there be more design options, besides bar charts with cropped axes, that Datawrapper deems unacceptable? And are they limited to chart designs that are outright misleading, or do they more generally ban designs that result in ineffective or inaccurate data communication? Here’s an exploration of Datawrapper’s bad graph policy.
Y-axis not starting at zero
Datawrapper disapproves of y-axes that don’t start at zero in bar and column charts, but it allows them in line charts. I think this is consistent with the consensus on the topic.
I’m using the term spaghetti chart in the non-technical sense, meaning a chart with many lines that create an indecipherable mess. Datawrapper doesn’t ban spaghetti charts.
Long the chart type we all loved to hate, the pie chart has recently been sort of rehabilitated. I think many people would now agree that pie charts are a legitimate way to represent proportions. That said, 3D and exploding pie charts are still suspect. Datawrapper allows pie (and donut) charts, but doesn’t seem to allow 3D or exploding pie charts.
Using perspective to create a 3D effect will make it difficult to compare the sizes of elements in a chart. Fortunately Datawrapper doesn’t seem to allow any type of 3D chart.
Stacked bar chart
The rehabilitation of the pie chart coincided with a renewed critique of stacked bar charts: «basic bar charts are clearly better than pie charts, but stack them and they’re worse!». Which, by the way, doesn’t mean that it’s always wrong to use stacked bar charts. Datawrapper allows them.
Some charts have have a secondary y-axis, so different scales can be used in one chart (here’s an awkward example, source). There may be situations where this is defensible, but in general it shouldn’t be considered good practice. Datawrapper doesn’t seem to allow this.
Pictograms instead of bars
Some designers try to jazz up bar charts using pictograms instead of bars, forgetting to take into account that if you double the height of the pictogram, its area increases fourfold. The distortion is even worse when the pictograms are drawn to appear three-dimensional. Datawrapper doesn’t seem to allow replacing bars with pictograms.