散点图把值编码为两个定量轴上点的位置。赫歇尔点绘轨道；高尔顿 1880 年代回归使该形式成名。
工作报告、广告与作业中适合两个度量的相关、离群与聚类。若一轴非定量，或时间才是主线，换一种形式。
Rules
- 规则 1 — Use 两个定量轴上点的位置 as one channel, not two.
- 规则 2 — Direct labels beat a distant legend.
- 规则 3 — Do not hide zero. If you break the axis, say so.
- 规则 4 — Colour encodes category or magnitude, not both.
- 规则 5 — Put the claim in the title, not just “散点图”.
- 规则 6 — Source and period, even in small type.
Palette
- 色板 1 — Categories: distinct hues. Sequences: one hue, changing value.
- 色板 2 — Diverging: a neutral centre, emphasis at both ends.
- 色板 3 — One brand colour plus greys beats a rainbow.
- 色板 4 — Check contrast on a projector and in greyscale print.
Type
- 文字 1 — Tabular figures for numbers. Do not pour body copy into the chart.
- 文字 2 — Titles as sentences; axes as short nouns.
- 文字 3 — For CJK, drop weight one step and leave tracking.
散点图: honour 两个定量轴上点的位置, and switch when 一轴非定量，或时间才是主线.