Spline Series
Spline Series draws a smoothed line using Bezier curve interpolation between data points. Used to see the trend clearly in noisy sensor data.
Prerequisite
This chart type can only be selected in step 2 of the Cartography Widget Wizard. If you have not started widget creation, start the wizard first; an appropriate Compass record is also required.
When to Use
| Scenario | Why Spline? |
|---|---|
| Raw vibration sensor data | Noise creates visual clutter |
| Atmospheric pressure trend | Smooths out small fluctuations |
| Slowly changing process parameter | Curve is easier to read |
Spline's Limitation
Spline does not change the actual values, but it draws fictional values between data points. If sudden, sharp changes (alarms, set point transitions) must be shown, prefer Line Series — sharp corners should not be hidden.
Data Structure
Same as Line Series:
| Column | Type | Example |
|---|---|---|
| X column | TIMESTAMP / TEXT |
ts, hour |
| Y column | NUMERIC |
vibration_g, pressure_bar |
Wizard Configuration
Step 5 — Series Design
Spline shares the same series design fields as Line (color, marker, stroke width). In addition:
| Field | Description |
|---|---|
| Spline Type | Natural (smooth) / Monotonic (monotonic-preserving) |
The Monotonic option prevents the curve from dipping when the value goes up; prefer it for monotonically increasing data such as production count.
Tips
- If data points are sparse (< 20 points), Spline makes a visual difference. With dense data the difference vs Line is small.
- For Spline + Area combinations, use Stacked Area or Area; Spline type has no fill.
9-Step Summary — Spline Series
Spline Series uses the Standard Cartesian flow.
| # | Step | Key point for Spline | Details |
|---|---|---|---|
| 1 | Group Selection | Cartesian | → |
| 2 | Chart Type | Spline Series card | → |
| 3 | Compass Record | Ordered X column (smoothing on noisy data) | → |
| 4 | Axis Config | X: DateTime/Numeric, Y: Numeric | → |
| 5 | Series Design | Spline Type (Natural/Monotonic), Marker | → |
| 6 | Add Series | Multiple series with secondary Y axis | → |
| 7 | General Design | Tooltip, Y Axis Suffix | → |
| 8 | Card Design | Refresh: 30-60s (SQL), 0 (MQTT) | → |
| 9 | Display | Name, Tags, Folder | → |
→ Standard Cartesian Flow overview