adding more nodes

docs/nodes/Relate Fields.md

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+# Relate Fields
+
+Fit a functional relationship between two data fields: b = f(a). Outputs the predicted field_b from the fit and a table of fitted parameters with R-squared goodness-of-fit. Equivalent to Gwyddion's relate.c module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field_a | DATA_FIELD | Yes | Independent variable field |
+| field_b | DATA_FIELD | Yes | Dependent variable field |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| predicted | DATA_FIELD | Predicted field_b values from the fitted function |
+| fit_params | RECORD_TABLE | Fitted coefficients and R-squared statistic |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| function | dropdown | linear | Functional form to fit: linear, quadratic, cubic, power, or logarithmic |
+
+## Notes
+
+- **Linear**: b = slope * a + intercept. Reports slope and intercept.
+- **Quadratic**: b = a2*a^2 + a1*a + a0. Reports a2, a1, a0.
+- **Cubic**: b = a3*a^3 + a2*a^2 + a1*a + a0. Reports a3, a2, a1, a0.
+- **Power**: b = c * a^n (fitted via log-log regression). Reports exponent and coefficient. Requires positive values in both fields.
+- **Logarithmic**: b = log_coeff * log(a) + intercept. Requires positive values in field_a.
+- R-squared is always reported as the last row: values near 1.0 indicate a good fit.
+- Both fields are flattened and truncated to the shorter length when they differ in total pixel count.
+- The predicted output retains field_b's shape and metadata.