Data Viz Daily

One chart critique or visualization decision a day for clearer analytical storytelling.

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Today's question

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What does Edward Tufte's data-ink ratio principle recommend?

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Oct 25
You are showing average annual temperatures for ten cities, where all values cluster between 15 and 25 degrees and zero has no special meaning. Which chart is most appropriate?
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Oct 24
Which of these is the most effective title for an analytical chart in a report?
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Oct 23
A chart shows the mean of two groups with 95 percent confidence interval error bars that overlap slightly. What can be concluded about the difference between the groups?
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Oct 22
Which colour pairing is most likely to be indistinguishable for readers with the most common form of colour vision deficiency?
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Oct 21
You need to compare the growth of several stocks with very different price levels on one line chart. What is the standard approach?
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Oct 20
A chart's vertical axis is labelled 'Revenue' with tick values of 1.2, 1.5, and 1.8. What is missing?
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Oct 19
You want to compare ten categories at two points in time, emphasising how much each changed and whether their ranking shifted. Which chart is best suited?
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Oct 18
What guidance did William Cleveland give for choosing the aspect ratio of a line chart?
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Oct 17
Why do visualisation guidelines advise against 3D bar charts for ordinary data?
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Oct 16
In a stacked area chart, which series can readers judge most accurately?
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Oct 15
A conversion rate rose from 10 percent to 12 percent. Which description is correct and unambiguous?
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Oct 14
A multi-line chart places its legend in a box far from the lines, forcing readers to look back and forth to match colours. What is the improvement?
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Oct 13
A choropleth map shades each region by the total number of reported cases of something. What is the main problem with this design?
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Oct 12
A pie chart has fourteen slices, many of them thin and similar in size. What is the better choice?
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Oct 11
In a bubble chart, which property of each circle should be proportional to the value it represents?
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Oct 10
A bar chart shows a metric for twelve countries listed in alphabetical order. What change would most improve comparison?
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Oct 9
Why is a rainbow colour palette discouraged for encoding continuous data such as elevation or temperature?
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Oct 8
You are colouring a map of temperature anomalies, with values above and below a zero baseline. Which type of colour palette is appropriate?
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Oct 7
Why are dual y-axis line charts frequently criticised as misleading?
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