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docs/nodes/Trimmed Mean.md

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+# Trimmed Mean
+
+Apply a local trimmed-mean filter to a DATA_FIELD. Within each circular window, the lowest and highest fraction of pixel values are excluded before computing the mean. This provides smoothing that is more robust to outliers than a plain Gaussian or mean filter. Equivalent to Gwyddion's `trimmed-mean.c` module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input field to filter |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| filtered | DATA_FIELD | Trimmed-mean filtered field |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| radius | INT | 3 | Radius of the circular filter window in pixels (1–50) |
+| trim_fraction | FLOAT | 0.1 | Fraction of values to exclude from each end of the sorted window (0.0–0.49) |
+
+## Notes
+
+- A trim_fraction of 0.0 gives a plain local mean (no trimming). A trim_fraction approaching 0.5 converges to the local median.
+- Typical values of 0.05–0.2 effectively suppress outlier spikes while preserving smooth features better than a median filter.
+- The filter uses a circular (disc-shaped) kernel; the actual window diameter is 2*radius + 1 pixels.
+- More computationally expensive than a Gaussian filter due to the sorting step within each window.