Change over time
Step / staircase chart
Shows a value remaining constant between discrete changes.
- Chart
- Trend over time
- Change between points
What it answers
When does a held value change?
- Shape
- Horizontal and vertical steps
- What it shows
- Change timing and duration at each level.
Example
The question
When did the price of our main product change, and by how much?
List price of the Standard plan, 2025 (EUR per month)
Illustrative data. It belongs to no company.
When to use it
Use it when
Prices, rates or inventory levels held constant between changes.
Avoid it when
Continuously varying measurements that are not stepwise.
How to read it
Read flat segments as unchanged values and vertical steps as updates.
Note
Specify whether changes apply before or after the timestamp.
The data you need
- Layout
- Long table
- Fields
- Time: date/datetime or ordered number; Value: number
- One row is
- One observation at a time or ordered position. What is the grain?
- Rules
- Parse dates consistently and sort ascending. Resolve duplicate timestamps by a declared rule. Missing values are not automatically zero.
- Optional
- Optional Series. Use regular spacing for methods requiring it.
- Preparation
- Parse and sort timestamps or sequence positions; aggregate duplicates deliberately and preserve gaps. Parse dates consistently and sort ascending. Resolve duplicate timestamps by a declared rule. Missing values are not automatically zero.
- 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 day 1=10, day 4=15, day 7=12. Hold each value until the next date. The level stays 10 on days 1-3.
| Time | Value |
|---|---|
| 2026-01-01 | 30 |
| 2026-02-01 | 34 |
| 2026-03-01 | 38 |