Hanging things on your charts

The Financial Times published the following chart that shows the rollout of vaccines in the U.K. (I can't find the online link to the article. The article is titled "AstraZeneca and Oxford face setbacks and success as battle enters next phase", May 29/30 2021.) This chart form is known as a "streamgraph", and it is a stacked area chart in disguise.  The same trick can be applied to a column...

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One of the most frequently produced maps is also one of the worst

Summer is here, many Americans are putting the pandemic in their rear-view mirrors, and gas prices are soaring. Business Insider told the story using this map: What do we want to learn about gas prices this summer? Which region has the highest / lowest prices? How much higher / lower than the national average are the regional prices? How much has prices risen, compared to last year, or compared to...

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Did prices go up or down? Depends on how one looks at the data

The U.S. media have been flooded with reports of runaway inflation recently, and it's refreshing to see a nice article in the Wall Street Journal that takes a second look at the data. Because as my readers know, raw data can be incredibly deceptive. Inflation typically describes the change in price level relative to the prior year. The month-on-month change in price levels is a simple seasonal adjustment used to...

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Start at zero improves this chart but only slightly

The following chart was forwarded to me recently: It's a good illustration of why the "start at zero" rule exists for column charts. The poor Indian lady looks like a midget in this women's club. Is the average Indian woman really half as tall as the average South African woman? (Surely not!) The problem is only superficially fixed by starting the vertical axis at zero. Doing so highlights the fact...

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Distorting perception versus distorting the data

This chart appears in the latest ("last print issue") of Schwab's On Investing magazine: I know I don't like triangular charts, and in this post, I attempt to verbalize why. It's not the usual complaint of distorting the data. When the base of the triangle is fixed, and only the height is varied, then the area is proportional to the height and thus nothing is distorted. Nevertheless, my ability to...

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Further exploration of tessellation density

Last year, I explored using bar-density (and pie-density) charts to illustrate 80/20-type distributions, which are very common in real life (link). The key advantage of this design is that the most important units (i.e. the biggest stars/creators) are represented by larger pieces while the long tail is shown by little pieces. The skewness is encoded in the density of the tessellation. So when the following chart showed up on my...

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Plotting the signal or the noise

Antonio alerted me to the following graphic that appeared in the Economist. This is a playful (?) attempt to draw attention to racism in the game of football (soccer). The analyst proposed that non-white players have played better in stadiums without fans due to Covid19 in 2020 because they have not been distracted by racist abuse from fans, using Italy's Serie A as the case study. The chart struggles to...

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Stumped by the ATM

The neighborhood bank recently installed brand new ATMs, with tablet monitors and all that jazz. Then, I found myself staring at this screen: I wanted to withdraw $100. I ordinarily love this banknote picker because I can get the $5, $10, $20 notes, instead of $50 and $100 that come out the slot when I don't specify my preference. Something changed this time. I find myself wondering which row represents...

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Tip of the day: transform data before plotting

The Financial Times called out a twitter user for some graphical mischief. Here are the two charts illustrating the plunge in Bitcoin's price last week : (Hat tip to Mark P.) There are some big differences between the two charts. The left chart depicts this month's price actions, drawing attention to the last week while the right chart shows a longer period of time, starting from 2012. The author of...

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Did the pandemic drive mass migration?

The Wall Street Journal ran this nice compact piece about migration patterns during the pandemic in the U.S. (link to article) I'd look at the chart on the right first. It shows the greatest net flow of people out of the Northeast to the South. This sankey diagram is nicely done. The designer shows restraint in not printing the entire dataset on the chart. If a reader really cares about...

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