Heatmap Settings
The Heatmap card controls how the interpolated surface is computed and rendered.
Interpolation Method
The visual estimates the value at every pixel by interpolating from the sample points. Three algorithms are available:
| Method | Description | Best For |
|---|---|---|
| IDW (Inverse Distance Weighting) | Each pixel is a weighted average of all samples; weight decreases with distance raised to a configurable power | General-purpose; smooth results with moderate point counts |
| RBF (Radial Basis Function) | Gaussian-weighted Shepard interpolation with a bandwidth parameter that controls how far each sample's influence spreads | Datasets where influence should drop off more steeply beyond a certain radius |
| Bilinear | Piecewise-linear interpolation over a Delaunay triangulation of the sample points | Edge-preserving results; exact at sample locations |
Choosing a method
Start with IDW (the default). If the surface looks too "spiky" around isolated points, increase IDW Power or switch to RBF and reduce the bandwidth. Use Bilinear when you want a faceted look that preserves linear gradients between neighbouring samples.
Interpolation Properties
| Property | Description | Default |
|---|---|---|
| Interpolation Method | IDW, RBF, or Bilinear | IDW |
| IDW Power | Exponent applied to distance in the IDW formula. Higher values make the influence of each point fall off faster, sharpening local peaks. | 2 |
| RBF Bandwidth | Gaussian sigma expressed as a percentage of the shorter plot dimension. Smaller values create narrower influence zones; larger values smooth more aggressively. | 15% |
| Grid Resolution | Side length (in pixels) of each interpolation cell. Smaller values produce a finer surface but increase render time. | 4 px |
Minimum sample count
At least 3 sample points are required to render the heatmap. With fewer points the visual displays an empty state message.