# Scale 1D curve to reference (compute-only)

## Summary
Compute scale factor between two 1D curves using robust least squares.

## Metadata
- **Module ID:** FindScaleFactor1D
- **Module path:** /home/runner/work/MoDaCor/MoDaCor/src/modacor/modules/base_modules/find_scale_factor1d.py
- **Module version:** 20251212.2
- **Keywords:** scale, calibration, 1D

## Required data keys
- signal

## Modifies
- **scale_factor**: signal, uncertainties, units
- **scale_background**: signal, uncertainties, units

## Required arguments
- _None_

## Default configuration
```json
{
  "background_output_key": "scale_background",
  "fit_background": false,
  "fit_max_val": null,
  "fit_min_val": null,
  "fit_val_units": null,
  "independent_axis_key": "Q",
  "interpolation_kind": "linear",
  "require_overlap": true,
  "robust_fscale": 1.0,
  "robust_loss": "huber",
  "scale_output_key": "scale_factor",
  "signal_key": "signal",
  "use_basedata_weights": true
}
```

## Argument specification
| Argument | Type | Required | Default | Description |
|---|---|---|---|---|
| `background_output_key` | str | No | scale_background | BaseData key to store the fitted background output. |
| `fit_background` | bool | No | False | Whether to fit a constant background offset. |
| `fit_max_val` | float or int or NoneType | No | - | Maximum x-value for the fit (in fit_val_units). |
| `fit_min_val` | float or int or NoneType | No | - | Minimum x-value for the fit (in fit_val_units). |
| `fit_val_units` | str or NoneType | No | - | Units for fit_min_val/fit_max_val if provided. |
| `independent_axis_key` | str | No | Q | BaseData key for the independent axis. |
| `interpolation_kind` | str | No | linear | Interpolation kind passed to scipy/numpy interpolation. |
| `require_overlap` | bool | No | True | Require overlapping x-range between reference and work data. |
| `robust_fscale` | float or int | No | 1.0 | Robust loss scale parameter. |
| `robust_loss` | str | No | huber | Robust loss function name for the fit. |
| `scale_output_key` | str | No | scale_factor | BaseData key to store the scale factor output. |
| `signal_key` | str | No | signal | BaseData key for the dependent variable signal. |
| `use_basedata_weights` | bool | No | True | Use BaseData weights when fitting. |