Darker cells mean a higher score for this topic on that metric.
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Quick answers
When should I pick Heatmap?
When the story is: patterns across two categorical axes at once.
When should I avoid Heatmap?
Skip it in cases like: precise lookup of a number, or a rainbow that is not color-blind safe.
Who invented or popularised it?
Toussaint Loua’s 1873 crime tables; later Toussaint/Bertin and 1990s gene arrays
What does it encode?
color value of a cell in a row-column grid
Is it OK in ads?
Yes if one claim is visible at a glance in Meta, Google and retail print; otherwise link to a full figure.
Will a teacher accept it?
Yes for lab reports and poster boards if axes, units and a source line are present.
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.
Make shapes, diagrams and charts in the browser. Download SVG or PNG — nothing is uploaded.
Work
- Work 1 — PowerPoint weekly: Heatmap for patterns across two categorical axes at once.
- Work 2 — One Heatmap on a quarterly bridge or KPI tile — not four.
- Work 3 — Build in Excel or Google Sheets, export SVG/PDF rather than a screenshot.
Ads
- Ads 1 — Meta, Google and retail print: one number, one shape, one arrow.
- Ads 2 — Keep callouts inside safe zones. No type in cropped corners.
- Ads 3 — If Heatmap will not fit a banner, keep the number and show the chart on the landing page.
School
- School 1 — lab reports and poster boards: does Heatmap answer the rubric?
- School 2 — Axis names, units, a source line. Markers read them.
- School 3 — Start with a mind map if you must; submit a figure that reads like Heatmap.
Steps
- Steps 1 — Write the claim in one sentence.
- Steps 2 — Check that Heatmap fits the claim. If not, switch.precise lookup of a number, or a rainbow that is not color-blind safe
- Steps 3 — Draw it flat in Excel or Google Sheets or PowerPoint.
- Steps 4 — Direct labels, faint grid, claim-title.
- Steps 5 — Check greyscale and a color-blind simulator.
- Steps 6 — Add source, period, units; export SVG/PDF.
Heatmap: honour color value of a cell in a row-column grid, and switch when precise lookup of a number, or a rainbow that is not color-blind safe.