So far, we’ve talked about a bunch of different visuals that people use quite a lot in reports. We also talked about their advantages, and disadvantages. Now, let’s talk about a graph that people use a lot, but is actually terrible, and you should never use it.
1 - Optical Illusion
There are many optical illusions that most people fall victim to. The easiest one is: ask someone if the length of a glass is bigger than the circumference, and most people will say yes. This is because the human eye can visually see the length, but it cannot see the whole circumference of the glass.
In a similar fashion, most people will automatically treat the color in the bottom right section as the biggest, in the pie chart below:
If you just skim the graph quickly, you’ll see that Supplier B (bottom right) is the biggest, however when the labels are added in, you’ll see that it’s actually supplier A that is the biggest (this has to do with the graph being 3d, and adding extra space on the bottom right for supplier B)
2 - The alternative
Recall from the last post that when it comes to visualizing different categories bar charts are the best. More specifically, horizontal bar charts are the best graphs that exist as of today for visualizing different categories. Here is what the above graph looks like, if it was done with a horizontal bar chart instead:
With bar charts, our eyes compare the end points. Because they are aligned at a common baseline on the left, it makes it easy to see every category’s relative size (a pie chart doesn’t have this advantage).
One thing that people like to say is that in a pie chart everything adds up to 100%. That is, if you add up each of the categories that it will add up to a total of 100%. Well…. you can do the same thing on a horizontal line graph, just rescale all of the values to percentages instead of raw numerics.
2.1 Donut Charts
If you’ve never seen a donut chart before, here is what they look like:
It’s like someone took a pie chart, and asked “How can we make it worse?”, and they came up with this. Obviously, don’t use it for any serious presentation.
3 - Never use 3D
If you are lazy you don’t have the read this whole section, you can just remember the quote below:
“Never Use 3D”
Recall from section 1. - Optical illusion, when you make a graph 3D, you give some of the categories extra space. This means the human eye will over-estimate some categories, and underestimate other ones.
On top of that, in a 3D graph, there are many unnecessary elements like side/floor panels. These elements cause a lot of distraction when the audience wants to actually read the information present in the graph.
On top of that, depending on the application you are using to create your graph, a lot of them have weird rules for how they even generate the bars for your graph. For example in MS Excel, the bar height is determined by an invisible tangent plane intersecting the corresponding height on the y axis. This ends up being a problem because when you are faced with similar values, the “3d” effect ends up making the bars lose their magnitude, and it’s hard to do a proper comparison. Here’s an example of a 3d chart in excel
Please don’t use 3d charts in any of your reports.