Change over time

Cumulative line chart

Plots accumulated amounts across ordered periods.

What it answers

How much has accumulated so far?

The question

Are we on track to reach the annual sales target?

Running total reaches 43.4 by September against a target path of 45; the full-year target is 60.

Illustrative data. It belongs to no company.

Tracking accumulated sales, arrivals or completions.

When inputs are already cumulative or rates are mistakenly summed.

Read the cumulative height at each point and changes between points.

Distinguish period amounts from already cumulative inputs.

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: Sort period amounts and calculate a running sum once. Do not sum already cumulative values again.
Units: Cumulative sum of additive period amounts, in their original unit. Do not add percentages or point-in-time balances without justification.

A long table: one row per observation, few columns. New data adds rows.

Period amounts 10,15,5 become cumulative 10,25,30. The final total is 30; period 2 contributes the largest increment.