折线图把值编码为沿有序时间的折线位置。威廉·普莱费尔 1786 年，后用于气象与市场。
工作报告、广告与作业中适合趋势、季节性与少量序列。若无序类别或超过约四条重叠序列，换一种形式。
Parts
- 标记 — The core mark of 折线图 is 沿有序时间的折线位置.
- 尺度 — The scale must show zero (or a declared break) and units.
- 轴 — Axis titles name the variable, not a mood.
- 图例 — A legend is weaker than a direct label. Write beside the mark when you can.
- 标签 — Numbers are optional. If comparison is the job, label the ends only.
- 网格 — Keep the grid faint. Data should own the ink.
- 注释 — One annotation sentence. Date the source.
- 外框 — A thin frame. Never a 3-D box.
Variants
- 时间序列 — Variant 1 of 折线图. Same encoding, different layout.
- 趋势线 — Variant 2 of 折线图. Same encoding, different layout.
- 普莱费尔折线 — Variant 3 of 折线图. Same encoding, different layout.
- 折线图 4 — Variant 4 of 折线图. Same encoding, different layout.
Labels
- 轴 — On 折线图, make Mark readable.
- 图例 — On 折线图, make Scale readable.
- 标签 — On 折线图, make Axis readable.
- 网格 — On 折线图, make Legend readable.
- 注释 — On 折线图, make Label readable.
折线图: honour 沿有序时间的折线位置, and switch when 无序类别或超过约四条重叠序列.