Change over time
Multiple-line chart
Shows separate series as lines on a shared ordered axis.
- Chart
- Trend over time
- Comparison
What it answers
How do series trends differ?
- Shape
- Multiple connected lines
- What it shows
- Divergence, convergence and crossovers.
Example
The question
How do monthly sales compare across three regions?
Sales per month by region, 2025 (EUR million)
Illustrative data. It belongs to no company.
When to use it
Use it when
Comparing a few time series with shared units.
Avoid it when
Many overlapping lines or incompatible measures without transformation.
How to read it
Follow one labelled line, then compare it with the others at matching dates.
The data you need
- Layout
- Long table
- Fields
- Time: date/datetime; Series: text; Value: number
- One row is
- One series observation at one time. What is the grain?
- Rules
- Sort time within series. Resolve duplicate time-series pairs and align series before stacking.
- Optional
- Wide alternative: Time,A,B with one row per time.
- Preparation
- Parse and sort timestamps or sequence positions; aggregate duplicates deliberately and preserve gaps. Sort time within series. Resolve duplicate time-series pairs and align series before stacking.
- Units
- Time uses a stated date/time unit and sampling period; the value axis uses the measure's unit. Rates need their own explicit denominator.
Worked example
Data A:30,34,38; B:45,40,35. Plot both. A rises while B falls; A is higher by March.
| Time | Series | Value |
|---|---|---|
| 2026-01-01 | A | 30 |
| 2026-01-01 | B | 45 |
| 2026-02-01 | A | 34 |
| 2026-02-01 | B | 40 |