

Why 3D pie charts are bad - bensummers
http://fury.com/2010/03/why-3d-pie-charts-are-bad/

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chaosmachine
So, for those that don't get it, this appears to be one of those self-
referential charts.

The percentage of blue pixels in the chart is shown by the red section of the
chart, and vice-versa (notice the labeling).

See also: <http://xkcd.com/688/>

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Roridge
yes I got it, I could still see which part was bigger.

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sh1mmer
but not very accurately. perspective is a bitch.

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lucifer
That is an isometric projection.

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barrkel
Pie charts, IMO, are almost never the correct choice. Even in cases where
there's a logical summation to 100%, absolute values (the size of the pie
altogether) is often also relevant; and pies with many slices are hard to
compare, when the angles for different slice shadings are at different
orientations.

Finally, too many charts rely on colour rather than patterns or markings to
distinguish choices. That usually makes them hard to read for colour-blind
people, as light shades of green and yellow, or dark blue and purple, etc. end
up being used.

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warfangle
People can quantify the difference between two lines of disparate length much
more easily than they can quantify the angle difference of slices of a pie
chart[1]. Pie charts are evil and should never be used. A full 86.1% of this
comment is fact; the rest is opinion.

[1]
[http://lilt.ilstu.edu/gmklass/pos138/datadisplay/badchart.ht...](http://lilt.ilstu.edu/gmklass/pos138/datadisplay/badchart.htm)

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Groxx
Personally, I dislike pie charts for that reason, plus they're hard to scan.
The text describing what area means what is floating all over, or connected by
a bunch of parallel lines, or (arguably better) mostly absent / in a legend.

Bar charts, especially horizontal, have skimmable labels. Pie charts do not.

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JulianMorrison
What are you using the graph for? If you're trying to convey information, a 3d
chart of any sort at all is less than effective. If nobody cares about the
information and you're going through the motions of a "presentation" for
merely corporate-cultural reasons, a 3d chart may add some useful bling.

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Vivtek
I think he's using the graph to demonstrate that pie charts suck. So his
choice of a pie chart was actually perfect.

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skilesare
Your brain doesn't see pixels. It sees volume. And it is really good at doing
so. You can process 1000x the amount of information in 3D that you can in 2D.
<http://aqumin.blogspot.com/>

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jcl
No, your brain sees pixels and guesses at volume. And it is spectacularly bad
at comparing the angles of a pie chart drawn in 3D perspective.

For example: [http://www.olivierlorrain.com/2010/02/21/data-
visualization-...](http://www.olivierlorrain.com/2010/02/21/data-
visualization-by-toby-segaran-webstock/)

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eapen
This is completely dependent on the angle that it is viewed from. IMO the 3D
pie chart should only be slightly angled so as to give a hint of a shadow but
not as extremely tilted as in this example. If it was tilted anymore and
depending on which side it was viewed from, you can make it completely red or
blue.

In other words, I like the irony but this is not really a good example.

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volare
_This is completely dependent on the angle that it is viewed from._

This is the author's point.

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FooBarWidget
Why is the Blue label pointing to the red region and the Red label pointing to
the blue region? Or are their lines actually pointing to the back of the chart
where you can't see the line ends?

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RiderOfGiraffes
You are being fooled, as pie charts often do.

There are more blue pixels in the image than red. This is because of the
thickness of the disk. Therefore in representing the proportion of blue pixels
it's more than half the area of the circle. Therefore he has one slice which
is more than half the area of the circle, and that half represents the blue
pixels. He colors that red.

And _vice versa._

The diagram is completely accurate, and very misleading. Adn deliberately so.
It can be difficult to get pie charts to represent data accurately, and in a
way that doesn't mislead the viewer.

On the other hand, correct use of pie charts can be very effective. It's just
that you don't often see it.

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wdewind
Have an example of correct use of pie charts?

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RiderOfGiraffes
I've just spent 20 minutes hunting, and the answer is "No, I have no examples
of correct uses of pie charts."

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Roridge
uh... why? I could see that the red part was bigger than the blue part.

THAT Pie chart was bad because of the legend being self representational, not
the isometric projection.

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bensummers
I think his point is that when you include the pixels which represent the
thickness of the disc, you inflate the apparent size of that slice.

So while you can clearly see the size of the elements, it requires thought and
interpretation. Compare to a 2D flat chart, which is very clear although not
so pretty. Shouldn't a visualisation require as little thought as possible?

I blame PowerPoint.

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Roridge
I actually got the point, I was saying that it was still obvious which part
was bigger, which is what a pie chart should be used for. Anything more
complex than that, and it's being used incorrectly.

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encoderer
The whole point of a chart is at-a-glance understanding of numbers and stats
that would normally take a more careful once-over.

And the whole point of a pie chart is to use one thing -- the size of a slice
-- to represent a single datum.

A 3d pie chart muddles both of those things for form-over-function reasons.
How is this even contentious? Pie charts are notoriously bad anyway,
especially if there's not a huge difference between the data points. This
makes them notably worse.

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Roridge
yeah... I get it... I could still see which part was bigger.

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ZeroGravitas
The purpose of a pie chart isn't to show which is bigger (which is much easier
to convey in text), but to give relative proportions.

So could you accurately estimate the two sizes? Research suggests you'd be
better off with a bar chart than with a pie chart except in certain cases (25%
vs 75%) and that isometric pie charts are worse than flat ones.

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qjz
It would be just as trivial to create a 3D bar chart that has the same effect
as the example (accurate, self-referential, and confusing because of the
color/label mismatch). While clever, this example isn't an indictment of pie
charts, because it clearly shows the relative proportions of two quantities
(as would a bar chart).

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ZeroGravitas
There's two different links in these comments that explain at length why pie
charts do not clearly show relative proportion. This is even less true of 3D
pies.

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hackermom
but we have to have more 3d. 3d is the current immersive property for a richer
viewer/user experience. and this needs to expand even to pie charts. the next
thing will be to add smell to the pie charts - so that they smell like pie.

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pavel_lishin
Wouldn't having the entire chart smell identically defeat the purpose?

You'd want the blue part smelling like blueberries, and the red part smelling
like strawberries.

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fburnaby
Well there's an easy solution here. Make the red smell like strawberry pie and
the blue like blueberry pie.

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mars
bleeh

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shrikant
I don't get it. So much for user experience design.

