SDM Gradient Heatmap
The SDM Gradient Heatmap renders a smooth, continuous color surface from a sparse set of XY sample points. Unlike tile-based heatmaps, values between samples are interpolated — the visual fills the entire plot area with a gradient rather than discrete colored cells.
Key Features
- Smooth interpolation — Three algorithms (IDW, RBF, Bilinear) to control how the surface is estimated between samples
- Color presets — Viridis, Turbo, Red-Yellow-Blue, Spectral, or fully custom min/mid/max colors
- Isolines — Contour lines at evenly-spaced value thresholds, with optional floating labels
- Sample point markers — Six shapes, configurable size, heatmap-derived or fixed colors
- Category labels — Smart multi-pass placement with leader lines, clustering, and word wrap
- Axes — X and Y axes with optional titles and manual range control
- Legend — Gradient color bar with auto-formatted tick labels (Right, Left, or Bottom)
- Cross-filtering — Click or Ctrl+click sample points to filter other visuals
- Tooltips — X, Y, Value, Category, and custom tooltip measures on hover
Data Wells
| Data Role | Description |
|---|---|
| X Axis | Numeric horizontal coordinate of each sample |
| Y Axis | Numeric vertical coordinate of each sample |
| Value | Numeric measure to interpolate across the surface (minimum 3 samples required) |
| Categories | Optional label/grouping field shown on sample point markers |
| Tooltips | Additional measures displayed in the hover tooltip |