Darker cells mean a higher score for this topic on that metric.
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Quick answers
When should I pick Line chart?
When the story is: trends, seasonality and a few series over time.
When should I avoid Line chart?
Skip it in cases like: unordered categories, or more than about four overlapping series.
Who invented or popularised it?
William Playfair, 1786 — later refined for meteorology and markets
What does it encode?
position of a polyline through ordered time
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.
Line chart encodes values as position of a polyline through ordered time. William Playfair, 1786 — later refined for meteorology and markets.
In reports, ads and assignments it fits trends, seasonality and a few series over time. Skip it when unordered categories, or more than about four overlapping series.
Principles
- Encoding — The core mark of Line chart is position of a polyline through ordered time.
- History — William Playfair, 1786 — later refined for meteorology and markets
- Fit — trends, seasonality and a few series over time
- Shared baseline — The eye compares length and position more accurately than area.
- Audience — PowerPoint, Excel or Google Sheets and Meta, Google and retail print share the same geometry.
Misconceptions
- Pretty equals true — Decoration rarely persuades; it slows reading.
- 3-D helps — Perspective distortion wrecks comparison. Keep it flat.
- More series is richer — Do not stack stories. One Line chart, one claim.
- Default palette is fine — Rainbow defaults fail color-blind viewers and grey print. Change Excel or Google Sheets defaults.
Why it matters
- Work — Work: trends, seasonality and a few series over time. Readable in four minutes in PowerPoint.
- Ads — Ads: one number and one shape speak first in Meta, Google and retail print.
- School — School: for lab reports and poster boards, pick the form that answers the rubric.
- Craft — Craft: honour position of a polyline through ordered time and decoration falls away.
Line chart: honour position of a polyline through ordered time, and switch when unordered categories, or more than about four overlapping series.