Heatmap encodes values as color value of a cell in a row-column grid. Toussaint Loua’s 1873 crime tables; later Toussaint/Bertin and 1990s gene arrays.
In reports, ads and assignments it fits patterns across two categorical axes at once. Skip it when precise lookup of a number, or a rainbow that is not color-blind safe.
This page gathers anatomy, fit, craft, failure modes and work / ads / school recipes for Heatmap.
Profile
Seven chapters
The idea
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. History. patterns across two categorical axes at once.
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Anatomy
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Mark. patterns across two categorical axes at once.
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When to use
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Fit. patterns across two categorical axes at once.
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Craft
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Rules. patterns across two categorical axes at once.
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Mistakes
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Failure modes. patterns across two categorical axes at once.
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Studio
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Work. patterns across two categorical axes at once.
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Tools
A matrix of intensity — dense, seductive, and easy to lie with a rainbow scale. Software. patterns across two categorical axes at once.
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Frequently asked questions
When should I pick Heatmap?
When should I avoid Heatmap?
Who invented or popularised it?
What does it encode?
Is it OK in ads?
Will a teacher accept it?
Which tool?
How do I keep it accessible?
Related
▭ Treemap
Hierarchy as nested rectangles — files, budgets and portfolios when a pie would choke.
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⚬ Scatter plot
Two measured variables as a cloud of points — the honest way to talk about correlation.
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📁 Work reports
The weekly and quarterly pack — bars, waterfalls and tiles that a manager can read in four minutes.
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