Time Series
Index Chart
Line chart rebased so every series starts at 100. Reads as 'normalized growth from baseline,' making relative change comparable across series of very different absolute magnitudes.
Stock Performance, Indexed to January 2025
All series rebased to 100 at Jan 2025; renderer marks the y=100 baseline directly
View data (36 rows)
| Date | Price | Stock |
|---|---|---|
| 2025-01 | 142 | AlphaCo |
| 2025-02 | 156 | AlphaCo |
| 2025-03 | 168 | AlphaCo |
| 2025-04 | 178 | AlphaCo |
| 2025-05 | 196 | AlphaCo |
| 2025-06 | 212 | AlphaCo |
| 2025-07 | 224 | AlphaCo |
| 2025-08 | 230 | AlphaCo |
| 2025-09 | 218 | AlphaCo |
| 2025-10 | 235 | AlphaCo |
| 2025-11 | 248 | AlphaCo |
| 2025-12 | 256 | AlphaCo |
| 2025-01 | 38 | BetaInc |
| 2025-02 | 36 | BetaInc |
| 2025-03 | 40 | BetaInc |
| 2025-04 | 39 | BetaInc |
| 2025-05 | 44 | BetaInc |
| 2025-06 | 49 | BetaInc |
| 2025-07 | 47 | BetaInc |
| 2025-08 | 45 | BetaInc |
| 2025-09 | 48 | BetaInc |
| 2025-10 | 50 | BetaInc |
| 2025-11 | 49 | BetaInc |
| 2025-12 | 47 | BetaInc |
| 2025-01 | 1240 | GammaLtd |
| 2025-02 | 1180 | GammaLtd |
| 2025-03 | 1100 | GammaLtd |
| 2025-04 | 1010 | GammaLtd |
| 2025-05 | 990 | GammaLtd |
| 2025-06 | 950 | GammaLtd |
| 2025-07 | 920 | GammaLtd |
| 2025-08 | 935 | GammaLtd |
| 2025-09 | 905 | GammaLtd |
| 2025-10 | 880 | GammaLtd |
| 2025-11 | 868 | GammaLtd |
| 2025-12 | 855 | GammaLtd |
Use an index chart when…
- Comparing relative growth across stocks, countries, products with different baselines
- When absolute units would obscure the percentage change story
- Performance dashboards normalized to a launch date
Avoid when…
- Absolute magnitude is the point
- Single series (use line chart)
- Non-time data
Data it needs
| Property | Value |
|---|---|
| Min Rows | 8 |
| Min Columns | 3 |
| Column Types | datestringnumber |
| Notes | Long format: date + series + value. Renderer rebases each series to 100 at its first observation. |
Visual anatomy
Marks
line
Channels
position-xposition-y (indexed)color-hue
Axes
x-timey-quantitative (index = 100)
Guiding principles
Consider instead
Common mistakes
Forgetting to mark the baseline (100) reference line
Choosing a baseline date that's an outlier
History
Common in financial reporting since the early 20th century; popularized in The Economist's growth charts.
Accessibility notes
State the baseline date in the subtitle. Describe each series' net change relative to 100.
Related reading
Got data? Let's see what works.
Drop your CSV. You'll get an Index Chart plus four alternatives - ranked by which one actually fits your data best.