time series

68 posts
Vaccine researchers discard the start-at-zero rule

I struggled to decide on which blog to put this post. The reality is it bridges the graphical and analytical sides of me. But I ultimately placed it on the dataviz blog because that's where today's story starts. Data visualization has few set-in-stone rules. If pressed for one, I'd likely cite the "start-at-zero" rule, which has featured regularly on Junk Charts (here, here, and here, for example). This rule only...

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Same data + same chart form  = same story. Maybe.

We love charts that tell stories. Some people believe that if they situate the data in the right chart form, the stories reveal themselves. Some people believe for a given dataset, there exists a best chart form that brings out the story. An implication of these beliefs is that the story is immutable, given the dataset and the chart form. If you use the Trifecta Checkup, you already know I...

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Making graphics last over time

Yesterday, I analyzed the data visualization by the White House showing the progress of U.S. Covid-19 vaccinations. Here is the chart. John who tweeted this at me, saying "please get a better data viz". I'm happy to work with them or the CDC on better dataviz. Here's an example of what I do. Obviously, I'm using made-up data here and this is a sketch. I want to design a chart...

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Illustrating differential growth rates

Reader Mirko was concerned about a video published in Germany that shows why the new coronavirus variant is dangerous. He helpfully provided a summary of the transcript: The South African and the British mutations of the SARS-COV-2 virus are spreading faster than the original virus. On average, one infected person infects more people than before. Researchers believe the new variant is 50 to 70 % more transmissible. Here are two...

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Reading an infographic about our climate crisis

Let's explore an infographic by SCMP, which draws attention to the alarming temperature recorded at Verkhoyansk in Russia on June 20, 2020. The original work was on the back page of the printed newspaper, referred to in this tweet. This view of the globe brings out the two key pieces of evidence presented in the infographic: the rise in temperature in unexpected places, and the shrinkage of the Arctic ice....

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A beautiful curve and its deadly misinterpretation

When the preliminary analyses of their Phase 3 trials came out , vaccine developers pleased their audience of scientists with the following data graphic: The above was lifted out of the FDA briefing document for the Pfizer / Biontech vaccine. Some commentators have honed in on the blue line for the vaccinated arm of the Pfizer trial. Since the vertical axis shows cumulative number of cases, it is noted that...

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Handling partial data on graphics

Last week, I posted on the book blog a piece about excess deaths and accelerated deaths (link). That whole piece is about how certain types of analysis have to be executed at certain moments of time.  The same analysis done at the wrong time yields the wrong conclusions. Here is a good example of what I'm talking about. This is a graph of U.S. monthly deaths from Covid-19 during the...

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These are the top posts of 2020

It's always very interesting as a writer to look back at a year's of posts and find out which ones were most popular with my readers. Here are the top posts on Junk Charts from 2020: How to read this chart about coronavirus risk This post about a New York Times scatter plot dates from February, a time when many Americans were debating whether Covid-19 was just the flu. Proportions...

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Atypical time order and bubble labeling

This chart appeared in a Charles Schwab magazine in Summer, 2019. This bubble chart does not print any data labels. The bubbles take our attention but the designer realizes that the actual values of the volatility are not intuitive numbers. The same is true of any standard deviation numbers. If you're told SD of a data series is 3, it doesn't tell you much by itself. I first transformed this...

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Is this an example of good or bad dataviz?

This chart is giving me feelings: I first saw it on TV and then a reader submitted it. Let's apply a Trifecta Checkup to the chart. Starting at the Q corner, I can say the question it's addressing is clear and relevant. It's the relationship between Trump and McConnell's re-election. The designer's intended message comes through strongly - the chart offers evidence that McConnell owes his re-election to Trump. Visually,...

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