Doughnut Pie

I was mortified at a recent conference organised by a big player in visualisation software (who shall remain nameless) to see an example dashboard sporting a hybrid doughnut-pie chart. The chart in question looked something like this:

In fact it was worse than this, I've tried to make the best of a bad chart by adding in some better practice around titles and labelling.

I think that there are four main things wrong with this chart:

• The linear distances for the pie chart are much shorter than those for the donut. For instance Segment B has a lower value in 2015 but a longer line when compared to 2014.
• Only the first and last segments can be compared directly between years as they have a commonly aligned point - the start of Segment A or the end of Segment E.
• There's no easy way to denote what the inner and outer sections represent. I've added this to the title as the best way that I could think to do it.
• As with all pie charts, the segments have to be coloured differently, preventing the use of colour to draw attention to key points.

I set about looking at alternatives to this chart, only to discover that Cole Nussbaumer Knaflic has been there before me looking at a similar problem on her excellent blog. Rather than create a poor reproduction of her thinking, I'd suggest having a read there.

Suffice it to say here that I decided upon a slope chart as the best way to convey the particular point that I chose to make with the data. With a slope chart every segment is easily comparable across the two years and it's possible to be sparing with colour to highlight a key point.

Incidentally, I did come across a doughnut pie that I feel I could get behind.