A table is nearly always better than a dumb pie chart; the
only worse design than a pie chart is several of them, for
then the viewer is asked to compare quantities located in
spatial disarray both within and between charts [...] Given
their low density and failure to order numbers along a
visual dimension, pie charts should never be used.
For instance, showing revenue breakdown while trying to explain that some department pulls more than the rest. Here, without normalization (via pie charts, percentages, stacked bars) it becomes more difficult to compare the ratios. This perfectly mirrors the idea of sufficient statistics for a particular inference.
I'll also argue that pie charts are still terrible ways to display "data of bounded measure". The primary arguments are (a) people are quite terrible at doing accurate comparisons with area or, worse, arglength and (b) it tends to destroy the consistency of you labels since there's not a clear preferred ordering in a pie chart.
In this case, I'd say that stacked bar charts or empirical empirical CDFs do a much better job displaying bounded data, and, if you can suffer removing the bound, then simple bar charts or dot plots do it best.
I'd be amazed to hear of a time that a pie chart is actually optimal. I think perhaps the best argument going forward is if ratios are sufficient for your story even with the labeling obscured (it just adds noise). Here, the ambiguity of the ordering on a pie chart might provide exactly the right vehicle.
I still wouldn't know whether it should be computed by arclength or area, though.
The use case you describe is actually quite common. If I have eight products and want to see at a glance which are contributing the most to my bottom line, a pie chart is perfect. The two conditions are met:
1) I'm looking at a meaningful total (all of my products)
2) I'm only interested in the ratios among them
To clarify, showing ratios is fine in a pie chart as long as the pie represents a meaningful total. If I just showed my top 3 products rather than all of them (or at least all of them in some explicit category), then using a pie chart would be inappropriate because there is no meaningful total; a bar chart or table would better in that case.
The top bar, which bounds the bars with the axis label 100% conveys the same 'from a whole' concept that the pie does in less space. Its also commutive across all three bars :-)
I agree with the OP and Tufte: something else is nearly always better than a pie.
Not too fan boy Apple too much but it is one of the few that uses pie charts effectively. But it is normally with only 2 or 3 pieces and usually to reinforce the difference in share.
For example, consider the voting pie charts earlier. Is it really helpful to notice that independents pick "other" a whole 1% more often than republicans? Because with a bar or labeled chart, you will pay attention to that.
So a stacked bar is mostly fine, but a scatter plot where the points are only distinguished by colour is impossible to read.
The problem lies in using a color-coded legend, not in using pie charts per se. The slices of a pie chart can be labelled directly (instead of indirectly via a legend), e.g.,
But I agree they are sometimes used when a bar graph would be much more appropriate.
That's more or less my philosophy on pie charts. I find them helpful to use at the outset of a presentation to help provide some context for what's to follow (for example, the relative sales of Divisions A, B & C).
That said, I have no sympathy for anyone who uses side-by-side pie charts in order to make comparisons.
* Start at 12 O'Clock
* Put the segments in sequence of size (smallest first or biggest first going clockwise)
* Add a legend or labels
* Make sure any colours you use can still be differentiated when printed greyscale
Honestly, I'd tolerate them more if I could just understand which segment was bigger than another segment and had some meaningful way in which to vaguely guess the value behind a segment.
Its not that you shouldn't use a pie chart, it is just about knowing when to use the pie chart to represent your data
In section 7.6 Plots and Charts the author explains very clearly the typical issues with bar diagrams and pie charts. Moreover, the whole chapter 7 Guidelines on Graphics is worth reading even for those who are not interested in the PGF package.
The PGF manual is one of the best introductions into that topic I'm aware of.
The example you give falls into the 'multiple pie chart' nightmare where it's hard to compare the percentages across charts. At the same time I can easily see how far from a majority each group is and also the pattern in abstaining from the question.
I frequently use combination of graphic, histogram and bar chart with one pie chart.
Graphics - for chronological data, pie chart - for absolute values.
He is very good at explaining Tufte's work. The best part of his books and website are comparisons between a typical charts or dashboards and his re-designs.
Following is more relevant, his article on pie charts (PDF): http://www.perceptualedge.com/articles/08-21-07.pdf
How do I know? Because they ask for them.
You're analysis for why pie charts are inferior at conveying information compared to other forms of data presentation are thus moot.
I'd like to think those are the source of the down votes--as I'd hate to believe we've forgotten the golden rule "customer is king". If their client comes to them and says "I want a pie chart" they should not give them 48 reasons why pie charts are terrible. They should just give them a pie chart.
I'm not suggesting that when ever they have data to convey their first thought should be to use a pie chart. I'm simply reminding them pie charts are a commonality of customer data visualization requests--hate them all they want they still will be using them.
Seriously... either explain your logic with supports or don't bother writing such misleading pieces of text.
- they fail to convey information because people have a really hard time judging relative areas instead of lengths.
- there are times when a pie chart is appropriate
- once you get data that isn't widely different or you have lots of categories your pie chart would be better as either a bar chart, or as simply a data table
- pic of horrid "word features" chart
- why is it bad?
- releases occur chronologically, but the data is displayed in a clockwise fashion with no obvious starting point
- the pie chart has no values on it at all, so we are left staring at the chart trying to guess the relative sizes of the slices
- the chart is 3D
- which makes it extra bad for estimating relative sizes
- 3D pie charts are simply an abomination
- making them 3D just makes them even harder to interpret
If you wanted to make a chart that looked impressive but contained as little information as possible, you'd have to work to do better than the pie chart.
Even a case of comparing A vs B is better represented by bars than pie slices.
Stacked bars may be ugly but at least you can use the segments to make more precise measurements.
Seriously, for any chart type, there are cases of misuse, even if the over-glorified Edward Tufte says no.