Bar chart encodes values as length of rectangles on one baseline. William Playfair, Commercial and Political Atlas, 1786.
In reports, ads and assignments it fits comparing a handful of categories at one time. Skip it when too many categories, 3-D extrusion, or dual-axis tricks.
Parts
- Mark — The core mark of Bar chart is length of rectangles on one baseline.
- Scale — The scale must show zero (or a declared break) and units.
- Axis — Axis titles name the variable, not a mood.
- Legend — A legend is weaker than a direct label. Write beside the mark when you can.
- Label — Numbers are optional. If comparison is the job, label the ends only.
- Grid — Keep the grid faint. Data should own the ink.
- Annotation — One annotation sentence. Date the source.
- Frame — A thin frame. Never a 3-D box.
Variants
- Column chart — Variant 1 of Bar chart. Same encoding, different layout.
- Category bars — Variant 2 of Bar chart. Same encoding, different layout.
- Playfair bars — Variant 3 of Bar chart. Same encoding, different layout.
- Bar chart 4 — Variant 4 of Bar chart. Same encoding, different layout.
Labels
- Axis — On Bar chart, make Mark readable.
- Legend — On Bar chart, make Scale readable.
- Label — On Bar chart, make Axis readable.
- Grid — On Bar chart, make Legend readable.
- Annotation — On Bar chart, make Label readable.
Bar chart: honour length of rectangles on one baseline, and switch when too many categories, 3-D extrusion, or dual-axis tricks.