Everyone is sick of talking about how pie charts suck. And whenever I do a charting post, it’s trouble. So this post is destined for failure. However, I was thinking about pie charts recently. I don’t have the disdain for pie charts that some do, but I generally agree with the majority of pie-haters that it is an overused and abused chart type. I think pie charts can be effective when you have two data points; three at most; never more than three.
Pie charts are difficult because they rely on area. When you go from one dimension to two, the one dimension is squared. It’s more difficult for humans to grok differences in area than differences in linear measurements. But let’s get to the pretty pictures. I stole some data from Seth Godin.
The purpose of this chart is to show that “Trolls” is big. And it does that. If your goal is to show how one data point relates to the whole, this works. It violates my “never more than three” rule, but the case could be made that there are only two data points here: Trolls and non-Trolls.
Doesn’t have quite the same impact, though. It appears that non-Trolls are more significant. If instead of comparing one data point to the whole, you want to compare data points to each other, the bar chart is the way to go.
Nothing wrong with that. In fact, I think it demonstrates Troll dominance even better than the pie. Back to my pie chart ruminations. What I was wondering why pie charts are round. That is, why do we show one-data-point-to-the-whole as a circle? It works just as well, or better, when we eliminate (or just fix) the second dimension.
I didn’t invent the square pie chart, but I can’t remember ever seeing it before. I wonder why it’s not a more common chart type. Someone once said, and I’m paraphrasing, “Pie charts are good when all of your data points are divisible by 25%”. Good point. I changed the above chart from values to percentages and added an axis with 25% as the major grid. People can relate to 25%, especially on a circle but even on a stacked bar.
So now you know what I think about. Scary, isn’t it? I’m going to start a movement to make the single-series-stacked-bar-in-lieu-of-pie chart more popular. But I need a name for it. Something that makes people feel as good as pie. Brownies are typically baked in square pans. Maybe I should call it a brownie chart.
Some details: To make a brownie chart, select stacked bar and on the Data Range tab, select the Rows option.
When you try to turn your data labels on end, the labels get cut off. I had to add four spaces to the front of the data and two to the end. I used this formula to transform the original:
What do you think? Are brownie charts the wave of the future?