Graphing Mistakes to Avoid Like the Plague!

I recently saw an alarming article on social media about an outbreak of airborne plague spreading from Madagascar to Africa (and potentially to the rest of the world). The plague?!? - I thought that only happened hundreds of years ago?!? I don't really trust news on Facebook, so I went to the CDCwebsite to verify, and sure enough there is currently an outbreak of pneumonic plague in Madagascar. This made me ask "how common or rare are cases of the plague in modern times, and where do these outbreaks occur?" Which of course seemed like a good topic for a graph!

But before we get into the data analysis, here's a picture of my friend Becky's daughter Jessie dressed as a plague doctor for Halloween. I'm happy to report that (at least so far) this suit has protected her from contracting the plague. :-)

Now, let's look at some plague data! I did a bit of Web searching, and found the following map which answered some of my questions. It showed where cases of the plague have been detected in the 21st century, and how many people have contracted it.

The map looked pretty good at first, but as I studied it I noticed several visualization problems -- things that you might want to "avoid like the plague" when creating your maps and infographics. (See what I did there?!?) Here's a list:

  1. The total number of plague cases is incorrect -- it is labeled as the total for the 12 countries, but it is actually the total for the world.
  2. The colors used for the countries and bubbles are not easy to distinguish, and match between the map and the legend.
  3. The colors of the plague countries, the non-plague countries, and the background blend in together, such that the countries with plague do not stand out as the main emphasis of the map.
  4. The country names are visually a long distance from the bubbles, and it's therefore difficult to determine which name goes with which bubble.
  5. The numbers in the bubble-legend are not lined up at the decimal point, therefore it's difficult to compare them.
  6. It's difficult to re-type the URL for the research study in the footnote.

In my version, I tried to fix all those problems. Also, you can click this link to see my interactive version, with html mouse-over text for everything in the infographic, and a drill-down link on the footnote so you can easily go to the research paper (without re-typing the URL).

  • I correctly state that the total number of plague cases shown in the red title is worldwide, not just the 12 countries in the map.
  • I use 4 discrete colors for the plague countries and the bubbles, therefore they are easy to match between the two.
  • The 4 colors I use for the plague countries are much brighter than the other colors in the infographic, making it easy to see that is the main point of the infographic. I also draw a darker outline around the plague countries, making them stand out.
  • I draw a dotted line between the legend bubbles and the country names, therefore it's easy to see which name goes with which bubble.
  • I align the numbers in the bubble legend, so they're easier to visually compare.
  • I make the URL in the footnote a drill-down link, so you can easily click on it to read the research study, without having to re-type it.

Hopefully you've learned a little about the plague, and also some tips about graphical mistakes to avoid -- indeed, things to "avoid like the plague!"

[This post originally appeared on the SAS Learning Post. Go there to read the original.]

Robert Allison, The Graph Guy!, SAS

Robert Allison has worked at SAS for more than 20 years and is perhaps the foremost expert in creating custom graphs using SAS/GRAPH. His educational background is in computer science, and he holds a BS, MS, and PhD from North Carolina State University. He is the author of several conference papers, has won a few graphic competitions, and has written a book calledSAS/GRAPH: Beyond the Basics.

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Re: Plague
  • 11/17/2017 10:19:33 PM

@Lyndon - this recent plague is scary. Saw an article that some people were dying from this sickness in just 3 hours. Yikes

Re: Plague
  • 11/16/2017 10:27:35 AM

Yes, it's pretty important to display any information up front about what a chart is depicting and there lies the problem with lots of graphics, it's just not clear what the basis for the statistics are, and thus the data can be manipulated to show a distorted picture.

Re: Plague
  • 11/16/2017 9:20:20 AM

I agree that the story might be different when viewed on a per capita basis. These diseases are largly diseases of the poor.

Re: Plague
  • 11/15/2017 11:58:58 PM

Legibility and colors are much improved.

I do wonder how the chart would look if it highlighted the top countries on a per-capita basis.

Even the Halloween costume is much better than the ordinary store-bought fare.

Avoiding visual confusion
  • 11/14/2017 8:32:02 AM

"The colors of the plague countries, the non-plague countries, and the background blend in together, such that the countries with plague do not stand out as the main emphasis of the map."


I don't know why but this is something I see more of lately.  I don't know if it's a graphic design lesson that people are following or if it is bleeding over from some other design concept but color palettes on charts like the example seem to be the norm.  While the colors for the plague outbreaks stand out it makes identifying things that they don't specifically call out for you a bit more difficult. 

Re: Plague
  • 11/13/2017 11:24:49 AM

In regard to the large-scale outbreak of pneumonic plague in East Africa, Huffington Post recently posted a particularly informative article:

Inside A Modern-Day Plague Outbreak


Re: Plague
  • 11/13/2017 8:22:54 AM

@sethbreedlove Yes, I know and there is also Google flu. I meant there are possiblities of adapting this form of visualization in particular -- not that we don't have access to data.

Re: Plague
  • 11/13/2017 2:35:33 AM

@ Ariella, for flue data there is an overwhelming amount of information.  The CDC creates weekly reports for the spread of the flue in the U.S and many other diseases.  The CDC is one of the few government organiztions in the U.S. that is on the ball as every political party sees its importance.   The World Health Orginazation is another great source of data. 

Re: Plague
  • 11/12/2017 11:51:24 AM

Perhaps this kind of visualization can be adapted to show the spread of other communicable diseases like flu. 

Re: Plague
  • 11/10/2017 5:35:43 PM

Another masterly graphic visualization improvement from Robert!

I'm also glad he's called attention to the African plague outbreak. I've been aware of this for a couple of weeks, and am shocked that it has not merited significant reporting in the mainstream media ...

Thanks to Robert for at least calling attention to this serious issue.


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